ENDOCRINOLOGY DEBORAH S. GRECO. Proudly Presents: With: DVM, PHD, DACVIM. Chicago Veterinary Medical Association

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1 Chicago Veterinary Medical Association Shaping the Future of Veterinary Medicine - Promoting the Human-Animal Bond Proudly Presents: ENDOCRINOLOGY With: DEBORAH S. GRECO DVM, PHD, DACVIM June 18, 2014

2 Chicago Veterinary Medical Association June 18, 2014 Managing the OBESE DIABETIC CAT Deborah S. Greco, DVM, PhD, DACVIM Nestle Purina Petcare Diabetes mellitus is one of the most common feline endocrine diseases, affecting one in every 200 to 300 cats. 1 Despite the increasing frequency of the disease, treatment of diabetic cats can be frustrating, and many patients experience such complications as hypoglycemia and progressive neuropathy. 2-7 The latest clinical and histologic evidence now suggests that type 2 diabetes mellitus is the most common form of diabetes affecting cats and people. 2-4 PATHOGENESIS OF TYPE 2 DIABETES MELLITUS In cats, diabetes mellitus is characterized by an impaired ability to secrete insulin following a glucose stimulus and is caused by both a defect in pancreatic beta cells and by peripheral insulin resistance. 2-4 It is now recognized that these classic metabolic abnormalities found in type 2 diabetes mellitus may be consequences of abnormal amyloid production by pancreatic cells and by secretion of hormones from adipose tissue. 2-4 Both the amount and distribution of adipose tissue play a role in insulin resistance and other obesity-related disorders. Resistin, a hormone produced by central adipose tissue and certain gastrointestinal cells, is an important link between adipose tissue and glucose homeostasis. Studies have shown that resistin increases hepatic glucose output even when insulin levels are high. This is the earliest change in type 2 diabetic people and cats. Adipose tissue also secretes the hormone adiponectin, which directly increases fatty acid transport, oxidation, and dissipation in skeletal muscle and, therefore, results in reduced levels of intramyocellular lipids, which improve insulin signaling. Adiponectin also increases hepatic insulin sensitivity either directly or indirectly by lowering circulating lipids via its action on muscle. The synthesis and secretion of adiponectin is reduced by caloric excess, and adiponectin administration results in improved insulin sensitivity and glucose tolerance associated with obesity. Finally, leptin resistance is found in early type 2 diabetes as a result of an increase in visceral abdominal tissue. Obesity and early type 2 diabetes also affect insulin sensitivity. Obese cats have low GLUT-4 (insulin sensitive glucose transporter) expression in both muscle and adipose tissue; however, the expression of GLUT-1 (insulin insensitive glucose transporter) is similar in lean and obese cats. 8 A decrease in GLUT-4 transporters occurs early in the course of diabetes development and could help identify which cats will develop clinical disease. Insulin secretion is affected early in the course of type 2 diabetes mellitus in people, particularly glucosemediated insulin secretion. The glucose transporter in pancreatic beta cells is GLUT-2. A decreased expression of these transporters causes a loss of the first phase of insulin secretion but normal second phase of insulin secretion similar to what is seen in later stages of obesity in cats (and people). Insulin resistance in beta cells may also lead to a decrease in insulin secretion. Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 1 of 60

3 Chicago Veterinary Medical Association June 18, 2014 In some forms of diabetes, a mutation of the glucokinase enzyme may lead to impaired insulin secretion in people. In animals and people, glucokinase converts glucose to glycogen for storage in the liver and is important in mopping up excess postprandial glucose. Normal cats that are deficient in glucokinase are similar to diabetic people in which glucokinase levels drop precipitously with persistent hyperglycemia from type 2 diabetes mellitus. DIAGNOSIS The early clinical signs of diabetes are almost nonexistent. In fact, the only signs that a cat may be developing type 2 diabetes mellitus are obesity and an increased appetite (from leptin resistance). As the disease progresses to affect insulin secretion and to cause insulin resistance, diabetic neuropathy and possibly nephropathy begin to appear. Diabetic neuropathy typically affects the hind limbs and can cause inappropriate elimination. This can be caused by an inability to climb in and out of the litter box, particularly if the box has tall sides, or it s not easily accessible (e.g., placed far away or at the bottom or top of stairs). Cats affected with diabetic neuropathy also can have trouble jumping onto high surfaces, such as counters and beds. Finally, diabetic neuropathy in people is associated with a variety of paresthesias and an inability to sense changes in surface temperatures. This condition may lead to irritability in affected cats. In one study, clinical and nonclinical diabetic cats all suffered from subclinical forms of diabetic neuropathy as evidenced by impaired motor and sensory peripheral nerve conduction. 7 The late signs of diabetes mellitus are easily identified. As blood glucose concentrations exceed the renal threshold (which may be as high as 350 mg/dl in some cats), polyuria and secondary polydipsia become the primary clinical signs. Weight loss begins as a result of calories lost in glucose-laden urine. Non-specific gastrointestinal signs, such as anorexia and diarrhea, develop intermittently in diabetic cats. This is perhaps a result of an autonomic neuropathy. As the diabetes progresses, ketosis and hyperosmolality lead to vomiting and severe dehydration, and the cat will present in a mixed hyperosmolar ketotic crisis. For diabetic patients, clinical pathology abnormalities include hyperglycemia, glucosuria, and elevated serum fructosamine. Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 2 of 60

4 Chicago Veterinary Medical Association June 18, 2014 Unfortunately, cats are susceptible to stress-induced hyperglycemia, which makes interpretation of isolated elevated serum glucose values difficult. In general, elevated blood glucose (> 130 mg/dl or 7 mmol/l) and a normal fructosamine (< 300 µmol/l) is consistent with stress-induced hyperglycemia. In contrast, an increase in both glucose and fructosamine would be consistent with early type 2 diabetes mellitus. Other common findings on the serum chemistry profile include elevations of serum alkaline phosphatase and alanine amino transferase activities as a result of reactive hepatopathy and hepatic lipidosis, hyperlipidemia (triglycerides and cholesterol), and azotemia (either prerenal due to dehydration or renal associated with diabetic nephropathy). In cats with diabetic nephropathy, urine specific gravity may be decreased, and proteinuria is common. The presence of glucosuria may or may not be helpful in most situations, as stress can result in glucosuria. TREATMENT Diet The cat is an obligate carnivore; therefore, amino acids, rather than glucose, are the signal for insulin release in cats. 10 In fact, a recent study demonstrated more effective assessment of insulin reserve in cats using the arginine response test rather than a glucose tolerance test. 11 Another unusual aspect of feline metabolism is the increase in hepatic gluconeogenesis seen after a normal meal. Normal cats maintain essential glucose requirements from gluconeogenic precursors (i.e., amino acids) rather than dietary carbohydrates. As a result, cats can maintain normal blood glucose concentrations even when deprived of food for more than 72 hours, 10 and feeding has very little effect on blood glucose concentrations in normal cats. 2,12 When type 2 diabetes occurs in cats, these metabolic adaptations to a carnivorous diet can become harmful, leading to severe protein catabolism, and feeding a diet rich in carbohydrates may exacerbate hyperglycemia and protein wasting in these diabetic cats. People with type 2 diabetes mellitus are often instructed to restrict excess dietary carbohydrates, such as potatoes and bread, and to control obesity by caloric restriction. 13 Furthermore, people with type 2 diabetes Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 3 of 60

5 Chicago Veterinary Medical Association June 18, 2014 have been shown to have improved glycemic control and improvement in protein catabolism during weight loss when a low-energy diet (high-protein) was combined with oral hypoglycemic therapy. 14 A low-carbohydrate, high-protein diet that is similar to a cat s natural diet (e.g., mice) may ameliorate some of the abnormalities associated with diabetes mellitus in the cat. Initial studies using a canned high-protein/low-carbohydrate diet and the starch blocker acarbose have shown that in 58% of cats insulin injections could be discontinued, and those with continued insulin requirements could be regulated on a much lower dosage (1U twice a day total). 15 Comparison of canned high-fiber versus low-carbohydrate diets showed that cats fed low-carbohydrate diets were twice as likely to no longer require insulin injections. 16 Another study examining clinical cases of diabetes mellitus in cats fed a high-protein, low-carbohydrate food (Purina Veterinary Diets DM) showed that insulin dosage could be decreased by 50%, and 25% to 30% of cats could discontinue insulin altogether. 17 Caution should be used when initially changing from dry to canned foods, as insulin requirements may decrease dramatically. A reduction in insulin dosage may be required. Weight reduction also decreases insulin resistance, and cats should be fed no more than 50 kcal/kg of ideal body weight in two equal meals per day. Oral hypoglycemics Indications for oral hypoglycemic therapy in type 2 diabetic cats include normal or increased body weight, lack of ketonuria, no underlying disease (pancreatitis, pancreatic tumor), history of diabetogenic medications, and the owners willingness to administer oral medication rather than an injection. Diet should consist of low-carbohydrate/high-protein foods only. Cats with early type 2 diabetes are most likely to respond to any oral hypoglycemic agent. Sulfonylureas, such as glipizide, increase insulin secretion and improve insulin resistance. Because they provoke insulin release, sulfonylureas may promote progression of pancreatic amyloidosis. In cats, glipizide has been used to successfully treat diabetes mellitus at a dosage of 2.5 mg twice daily when combined with a highprotein, low-carbohydrate diet. The patient is evaluated weekly (urine glucose) or every two to four weeks (fructosamine) for a period of two to four months. Gastrointestinal side effects, which occur in about 15% of cats treated with glipizide, usually resolve when the drug is administered with food. 18 A new Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 4 of 60

6 Chicago Veterinary Medical Association June 18, 2014 sulfonylurea, glimepiride (Amaryl Aventis Pharmaceuticals) has recently entered the human market; this compound has fewer side effects than glipizide and may be dosed once daily at 2 mg per cat. Alpha-glucosidase inhibitors impair glucose absorption from the intestine by decreasing fiber digestion and the resulting glucose production from food sources. 19 These medications are not absorbed systemically and may be used in conjunction with other oral hypoglycemics or insulin. Acarbose may be used as the sole initial therapy in obese prediabetic patients suffering from insulin resistance or as adjunct therapy with sulfonylureas or insulin to enhance the hypoglycemic effect in patients with diabetes mellitus. I have had experience using acarbose at a dosage of 12.5 mg/cat twice a day administered with a meal. The glucoselowering effect of acarbose alone is mild with blood glucose concentrations decreasing only into the 250 to 300 mg/dl (14 to 17 mmol/l) range. However, acarbose is an excellent agent when combined with insulin to improve glycemic control. Side effects are rare with appropriate diet adjustments but, at high dosages, may include flatulence, loose stool, and diarrhea. Insulin Although all mammalian insulin is structurally similar, small differences in amino acid sequences may be found between species. Mammalian insulin is composed of 51 amino acids arranged in two polypeptide chains. 20 The A-chain contains 21 amino acids and the B chain contains 30 amino acids. PZI insulin is available as a beef-pork formulation (IDEXX Pharmaceuticals). Pork Lente insulin is available as Vetsulin (Intervet), but Ultralente is no longer available from any company. When contemplating a change in insulin source, consider that different types and brands have different pharmacologic properties. Synthetic insulins, such as Lantus (glargine), have been developed for use in human medicine. Preliminary research on glargine suggests that it has some advantages over PZI insulin in cats. In fact, recent studies have shown that a combination of glargine and a lowcarbohydrate, high-protein diet resulted in 100% remission of insulin dependence in newly diagnosed cats. Initial insulin doses range from 0.2 to 0.5 U/kg; however, most cats are readily managed on two units twice daily, as a starting dose. 22 If intermediate-acting insulin is used, it must be administered to cats twice daily because of its short duration of action. If PZI insulin is used, a once-daily starting dose of one to three units per Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 5 of 60

7 Chicago Veterinary Medical Association June 18, 2014 cat is often recommended. Glargine (Lantus insulin) should be used cautiously in cats to avoid hypoglycemia. A starting dose of one to two units twice daily is recommended, with careful blood or urine monitoring, to avoid hypoglycemic episodes. 22 The injection site should be discussed with pet owners, as insulin absorption differs from site to site. In animals, the back of the neck (scruff) is commonly used for insulin injection. However, this site is not recommended because of lack of blood flow and the potential for increased fibrosis caused by repeated injections at this site. Instead, the recommended injection sites are along the lateral abdomen and thorax. The owner should rotate the site of injection daily. Many commercially available pamphlets outline injection techniques, feeding, and hypoglycemic episode management, and they provide a log sheet for owners to record food intake, clinical signs, urine glucose measurements, and insulin dosages. MONITORING DIABETIC CATS Urine glucose Urine glucose monitoring may be performed at home by owners, is not affected by stress, and may indicate insulin-induced hyperglycemia (Somogyi effect) indicated by high urine glucose on repeated morning samples. Urine glucose is a measure of trends in blood glucose and should not be used alone to adjust insulin dosages. However, urine glucose should decrease to trace or one plus with appropriate therapy. Consistently high urine glucose indicates the need for blood glucose evaluation. It is vitally important that the client monitor the urine glucose when the cat is ready to go off insulin. This is best accomplished using the Glucotest system, a home urine glucose monitoring system for cats that allows clients to wean their pets off of insulin. The Glucotest packets can be sprinkled in the litter pan over premium clumping litter and checked daily for color change. Using this monitoring method to adjust diabetes treatment allows for approximately 70% of cats to be managed with little or no insulin (Table 1, page 2). Blood glucose Glucose monitors designed for home monitoring in people are inexpensive, accurate, rapid, and require only a drop of blood. Although reasonably accurate in the blood glucose range of 60 to 120 mg/dl (4 to 12.5 mmol/l), these monitors are designed to read lower than the actual value as glucose approaches the hypoglycemic range. Above 120 mg/dl, human monitors are not accurate. Such factors as altitude, oxygen therapy, patient hematocrit, shock, dehydration, severe infection, and out-of-date or improperly stored test strips, can all affect the monitors accuracy. Whole blood glucose concentrations are lower than serum glucose concentrations (because of the metabolism of glucose by red blood cells in whole blood), so veterinarians should consult the monitor manufacturer to determine suitability for feline patients. A veterinary glucose monitor marketed as the Abbott AlphaTRAK has the highest correlation to clinical laboratory sample glucose analysis, as shown in Figure 1 (page 3). The Bayer Ascensia Contour and the Roche AccuChek Advantage are both excellent human monitors, but fall short of the accuracy of the Abbott product when used in animals. It is very rare to obtain a perfect glucose curve in a single patient. In fact, blood glucose curves are good for identifying trends in blood glucose during the day and not very helpful in cats. Blood glucose curves contain information vital to maintaining or adjusting insulin dosages (Figure 2, page 4). Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 6 of 60

8 Chicago Veterinary Medical Association June 18, 2014 The glucose nadir is the lowest concentration of blood glucose on the curve and should occur approximately halfway through the dosing interval. For example, if insulin is administered every 12 hours, the nadir should fall 5 to 6 hours after the insulin dose. The time of the glucose nadir indicates the time of peak insulin action, and the ideal blood glucose curve should have a nadir between 100 to 150 mg/dl (5 to 8 mmol/l). The duration of insulin action is related to both the time of the glucose nadir and the absolute concentration of the glucose nadir, in that you cannot determine insulin duration until achieving the target glucose nadir concentration of 80 to 120 mg/dl (4 to 7 mmol/l). If the target glucose nadir is achieved approximately halfway through the dosing interval, the duration of action of insulin and, thus, the type of insulin used, should be adequate. The glucose differential is the difference between the absolute concentration of glucose at the nadir and the absolute concentration of glucose before the next insulin dose. The glucose differential should be less than 150 to 200 mg/dl (8 to 11 mmol/l) in cats. Generally, atypical blood glucose curves can be differentiated by the curve s characteristics and the insulin dosage (per dosing interval). If the patient is receiving > 2.2 U/kg of insulin per dose, insulin resistance should be investigated. Causes of insulin resistance in cats can include hyperthyroidism, hyperadrenocorticism, acromegaly, drug therapy, and infections. If the patient is receiving < 2.2 U/kg per dose, the blood glucose curve usually is indicative of one of the following: insufficient dosage of insulin, short duration of action of insulin, insulin-induced hypoglycemic hyperglycemia (Somogyi effect), or insulin overlap seen with prolonged insulin action. Corrective actions include, respectively, increasing the insulin dose, changing to a longer acting insulin or twice-daily insulin regimen, reduction of the insulin dose by 25%, or changing to a shorter-duration insulin or a mixture of insulin types. Glycosylated blood proteins Glycosylated blood proteins are indicative of mean glucose concentrations in serum over an extended period of time and may be used to monitor long-term insulin therapy. These proteins are particularly useful in monitoring diabetic cats that may be stressed by hospitalization and serial blood glucose curves. As plasma glucose concentrations increase, glycosylation of hemoglobin and serum proteins increases proportionately. Glycosylation of serum proteins, such as albumin, forms fructosamine. Because albumin has a shorter life span than hemoglobin, fructosamine concentrations reflect more recent changes (one to three weeks) in serum glucose concentrations than glycosylated hemoglobin concentrations. Fructosamine concentrations less than 400 to 450 µmol/l are associated with good to excellent glycemic control; concentrations of 450 to 550 µmol/l indicate fair to good control; and serum fructosamine greater than 550 µmol/l indicates poor glycemic control (Figure 3, page 5). Relative changes in serum fructosamine may be more helpful than absolute values in some cases. It is often helpful to interpret the serum fructosamine in concert with mid-day blood glucose concentrations. CONCLUSION Obesity is the primary cause of early type 2 diabetes mellitus in cats. This relationship of increased diabetogenic hormones, such as resistin and leptin, is important in the pathogenesis of insulin resistance and eventual clinical Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 7 of 60

9 Chicago Veterinary Medical Association June 18, 2014 signs of diabetes. Early diagnosis coupled with strict dietary regulation will result in improvement of the diabetic state and restoration of normal patterns of insulin secretion. In cats with more advanced early type 2 diabetes mellitus, the use of oral hypoglycemic agents along with a high-protein, low-carbohydrate diet will result in adequate diabetic control. Diabetic cats should be monitored for reversal of glucose toxicity and insulin dependence using at-home glucose monitoring, blood glucose curves (in some cases), and serum fructosamine. REFERENCES 1. Panciera D, Thomas CB, Eicker SW, et al. Epizootiologic patterns of diabetes mellitus in cats: 333 cases ( ). J Am Vet Med Assoc 1990;197: Rand JS. Management of feline diabetes. Aust Vet Pract 1997;27: O Brien TD, Butler PC, Westermark P, et al. Islet amyloid polypeptide: A review of its biology and potential roles in the pathogenesis of diabetes mellitus. Vet Pathol 1993;30: Lutz TA, Rand JS. A review of new developments in type 2 diabetes mellitus in human beings and cats. Br Vet J 1993; 149: Crenshaw KL, Peterson ME. Pretreatment clinical and laboratory evaluation of cats with diabetes mellitus: 104 cases ( ). J Am Vet Med Assoc 1996;209: Whitely NT, Drobatz KJ, Panciera DL. Insulin overdose in dogs and cats: 28 cases ( ). J Am Vet Med Assoc 1997;211: Munana KR. Long-term complications of diabetes mellitus, Part I: Retinopathy, nephropathy, neuropathy. Vet Clin North Am Small Anim Pract 1995;25: Brennan CL, Hoenig M, Ferguson DC. GLUT4 but not GLUT1 expression decreases early in the development of feline obesity. Domest Anim Endocrinol 2004;26: Ballard FJ. Glucose utilization in mammalian liver. Comp Biochem Physiol 1965;14: Kettlehut IC, Foss MC, Migliorini RH. Glucose homeostasis in a carnivorous animal (cat) and in rats fed a high-protein diet. Amer J Physiol 1978;239:R115- R Kitamura T, Yasuda J, Hashimoto A. Acute insulin response to intravenous arginine in nonobese healthy cats. J Vet Intern Med 1999;13: Martin GJW, Rand JS. Lack of correlation between food ingestion and blood glucose in diabetic cats, in Proceedings. 15th Ann Amer Coll Vet Int Med 1997; Unger RH, Foster DW. Diabetes mellitus. In: Wilson and Foster, eds. Williams textbook of endocrinology. Philadelphia, Pa: WB Saunders, 1998: Gougeon R, Styhler K, Morias JA, et al. Effects of oral hypoglycemic agents and diet on protein metabolism in type 2 diabetes. Diabetes Care 2000;23: Mazzaferro E, Greco DS, Turner AS, et al. Treatment of feline diabetes mellitus using an alpha-glucosidase inhibitor and a low-carbohydrate diet. J Feline Med Surg 2003;5: Bennett N, Greco DS, Peterson ME, et al. Comparison of a low carbohydrate-low fiber diet and a moderate carbohydrate-high fiber diet in the management of feline diabetes mellitus. J Feline Med Surg 2006;8: Frank G, Anderson W, Pazak H, et al. Use of a high protein diet in the management of feline diabetes mellitus. Vet Ther 2001;2: Ford S. NIDDM in the cat: treatment with the oral hypoglycemic medication, glipizide. Vet Clin North Am Sm Anim Pract 1995;25: Kahn CR, Shechter Y. Insulin, oral hypoglycemic agents and the pharmacology of the endocrine pancreas. In: Goodman Gilman A, Rall TW, Nies AS, et al, eds. The pharmacological basis of therapeutics. 8th ed. New York, NY: Pergamon Press, 1990; Smith L. Amino acid sequences of insulin. Diabetes Care 1972;21: Hallden G, Gafvelin G, Mutt V, et al. Characterization of cat insulin. Arch Biochem Biophys 1986;247: Greco DS, Broussard JD, Peterson ME. Insulin therapy. Vet Clin North Am Small Anim Pract 1995;25: Diehl KJ. Long-term complication of diabetes mellitus, Part II: Gastrointestinal and infectious. Vet Clin North Am Sm Anim Pract 1995;25: Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 8 of 60

10 Feline Adrenal Disorders Deirdre Chiaramonte, DVM, DACVIM,* and Deborah S. Greco, DVM, PhD, DACVIM Although only recently discovered, feline adrenal disorders are becoming increasingly more recognized. Feline adrenal disorders include diseases such as hyperadrenocorticism (Cushing s syndrome) and hyperaldosteronism (Conn s syndrome). The clinical signs of feline hyperadrenocorticism, which include unregulated diabetes mellitus and severe skin atrophy, are unique to the cat. Other signs of feline hyperadrenocorticism, such as potbellied appearance, polydipsia, polyuria, and susceptibility to infections are also seen in dogs with hyperadrenocorticism. Conn s syndrome has only recently been described in the cat and is in fact more common in cats than in dogs. Characterized by severe hypokalemia, hypertension, and muscle weakness, Conn s syndrome may be misdiagnosed as renal failure. The clinician should become familiar with the clinical signs of adrenal disorders in cats and the common diagnostic tests used to diagnose these syndromes in cats as they differ from those in the dog. Treatment of feline adrenal disorders may be challenging; the clinician should become familiar with common drugs used to treat adrenal disorders in cats. Clin Tech Small Anim Pract 22: Elsevier Inc. All rights reserved. KEYWORDS adrenal disorder, Cushing s syndrome, hyperadrenocorticism, Conn s syndrome Feline Cushing s syndrome (FCS) is a disorder of excessive cortisol secretion by the adrenal glands. FCS is most often caused by a pituitary adenoma with subsequent corticotrophic hyperplasia and excess adrenocortical cortisol secretion. 1-7 Also found in cats with FCS are autonomously functioning benign adenomas (50%) or malignant adrenal carcinomas (50%). 4,6 Iatrogenic FCS due to glucocorticoid administration is rare in cats. 8,9 Differential diagnoses include diabetes mellitus, insulin resistance, acromegaly, hepatopathy, renal disease, sex hormone-secreting adrenal tumors, and hyperthyroidism. 10 Age, Breed, and Sex Pituitary-dependent hyperadrenocorticism (HAC) is usually a disease of the middle-aged to older cat in the range of 5 to 16 years and a median age of 10 years. 1-7 There is a slight difference in sex distribution in feline HAC; female cats are slightly more (60%) likely to develop the disease than males. 3-5 No breed predilection has been found. History, Clinical Signs, and Physical Examination Feline HAC is usually (80%) accompanied by diabetes mellitus (DM). 10 The most common clinical signs associated with HAC *The Animal Medical Center, New York, New York. Nestle Purina Petcare, St. Louis, Missouri. Address reprint requests to Deirdre Chiaramonte, DVM, DACVIM, The Animal Medical Center, 510 East 62nd Street, New York, NY Deirdre.Chiaramonte@amcny.org in cats are insulin-resistant DM, cutaneous atrophy, polydipsia, polyuria, polyphagia, lethargy, abdominal enlargement or potbelly, panting, obesity, muscle weakness, and recurrent upper respiratory and urinary tract infections. 1-8 On physical examination, the most commonly noted abnormalities include abdominal enlargement, hepatomegaly, bilaterally symmetric alopecia, cutaneous atrophy with open sores, and seborrhea (Figs. 1-3). Lethargy (dullness) has been reported due to muscle weakness or the effects of a pituitary mass. Excess sex hormones, such progesterone, have also been identified in cats with FCS. 6,7 Routine Laboratory Findings In the dog, the most common serum chemistry abnormality observed in association with HAC is an increased serum alkaline phosphatase activity (ALP), which is high in 85 to 90% of dogs. 1-6 However, in the cat serum ALP is not elevated because of hypercortisolemia but rather is a result of poorly regulated concomitant DM. This occurs because cats lack the glucocorticoid-induced isoenzyme for ALP. High serum alanine transferase activity (ALT), hypercholesterolemia, hyperglycemia, and low blood urea nitrogen (BUN) are also common findings. The hemogram may reveal a mild erythrocytosis as well as a classic stress leukogram (ie, eosinopenia, lymphopenia, and mature leukocytosis). Although in dogs with HAC, the urine specific gravity is usually less than 1.015, cats often show concentrated urine specific gravity ( 1030) despite profound polydipsia and polyuria resulting from the concurrent DM. 11 Finally, many cats with HAC have evidence of urinary tract infection without pyuria (positive culture), bacteriuria, and proteinuria resulting from glomerulosclerosis /07/$-see front matter 2007 Elsevier Inc. All rights reserved. doi: /j.ctsap

11 Feline adrenal disorders 27 Figure 1 Cat with pituitary-dependent hyperadrenocorticism showing potbellied appearance. (Color version of figure is available online.) Screening Tests Urinary Cortisol: Creatinine Ratio The urine cortisol:creatinine ratio (UCCR) is a simple and valuable screening test for HAC in cats. 11 To perform this test, the owner is instructed to collect morning urine samples from an empty litter box at the same time of day on two to three consecutive days. Special precautions are needed for the urine collection itself (no contamination with litter) and the urine samples should be kept refrigerated. This home-collection protocol avoids the stress of a visit to the veterinary clinic. After submission of the cat s morning urine samples to the laboratory for determination of cortisol and creatinine con- Figure 2 Skin lesions in a cat with hyperadrenocorticism. (Color version of figure is available online.)

12 28 D. Chiaramonte and D.S. Greco Figure 3 Alopecia, rat tail, and pendulous abdomen in a cat suffering from hyperadrenocorticism. (Color version of figure is available online.) centrations, the veterinarian should average the results of the two to three UCCR. The mean urine UCCR differentiates between clinically normal cats and cats with HAC. A high mean cortisol:creatinine ratio will be found in most cats with hyperadrenocorticism; however, the cortisol:creatinine ratio is also high (false-positive) in many cats with nonadrenal illness. 11,12 A high cortisol:creatinine ratio in a cat with concurrent disease should be confirmed with a low-dose dexamethasone suppression test. Although the low-dose dexamethasone suppression test is typically performed by measuring serum or plasma cortisol concentrations before and after dexamethasone injection, measurement of UCCR in samples collected before and after administration of a low dose of oral dexamethasone has also been described. This protocol is described in the article on diagnosis of Cushing s syndrome in dogs by Peterson in this issue. Low-Dose Dexamethasone Suppression Test The low-dose dexamethasone suppression test is considered by many to be the test of choice for the diagnosis of HAC in cats. 3,4 It requires 10 times the dose used in dogs or 0.1 mg/kg IV. Plasma is obtained for cortisol concentrations before, 4 hours after, and 8 hours after dexamethasone administration. If the low dose of dexamethasone (0.1 mg/kg) fails to adequately suppress circulating cortisol concentrations in a cat with compatible clinical signs, this is consistent with a diagnosis of HAC. Normal cats and cats with nonadrenal illness will show adequate suppression of serum or plasma cortisol (ie, 1 \ 6 dg/dl or 30 nmol/l) at 4 and 8 hours post dexamethasone administration. However, in contrast to dogs with pituitary dependent hyperadrenocorticism (PDH), many cats with PDH will not suppress at 4 hours and a few cats will suppress at 8 hours after dexamethasone administration. Corticotropin (ACTH) Stimulation Test The ACTH stimulation test, mainly a test of adrenal reserve, requires little time, is easy to interpret, and can be used to document iatrogenic HAC. 6,13 Only 50 to 60% of cats with HAC have an exaggerated response to ACTH administration, with post-acth serum cortisol concentrations rising to greater than 16 \ 6 dg/dl ( 400 nmol/l). The preferred method for ACTH stimulation testing in cats is to determine serum cortisol concentrations 30 minutes before and 1 hour after the intravenous or intramuscular injection of cosyntropin (Cortrosyn, Amphastar Pharmaceuticals, Rancho Cucamonga, CA), administered at a dosage of at least 5 \ 6 dg/kg. 3,4,19,20 Differentiation Tests High-Dose Dexamethasone Suppression Test The high-dose dexamethasone suppression test (HDDST) is performed by administering a high dose of dexamethasone (1 mg/kg IV) in a protocol identical to the low-dose dexamethasone suppression test (LDDST). An at-home version using multiple UCCRs and oral dexamethasone is easier to perform and interpret than the in-hospital protocol. Plasma Endogenous ACTH Concentration Endogenous ACTH concentrations are normal to high in cats with pituitary-dependent HAC (eg, 80 pg/ml or 18 pmol/l), whereas ACTH concentrations are usually low or undetectable (eg, 20 pg/ml or 4.4 pmol/l) in cats with adrenal tumors or with iatrogenic HAC. Samples for accurate endogenous ACTH concentration determination must be collected in EDTA tubes and centrifuged immediately; the plasma is then placed into plastic or polypropylene tubes (ACTH will stick to glass) and immediately frozen until the assay is performed. Abdominal Ultrasonography As with the dog, ultrasonography can be used to differentiate between PDH from adrenal tumors in the cat. 14 Symmetric adrenal glands of normal or enlarged size are suggestive of PDH, whereas unilateral enlargement supports ATH. With

13 Feline adrenal disorders 29 abdominal ultrasonography, small or noncalcified unilateral adrenal tumors can generally be readily detected, and bilateral adrenal enlargement can be visualized in cats with pituitary-dependent HAC. 14 Ultrasonography may, in addition, detect the presence of liver metastasis or invasion of the vena cava from an adrenal carcinoma. The contralateral adrenal gland would be expected to be small in cats with unilateral cortisol-secreting tumor due to the fact that pituitary ACTH secretion has been chronically suppressed. Computed Tomography and Magnetic Resonance Imaging Computed tomography (CT) and magnetic resonance imaging (MRI) are reliable methods to image either the adrenals or the pituitary glands. 15 As with dogs, bilateral adrenal enlargement can be readily differentiated from a unilateral adrenal tumor in most cats. CT or MRI is most helpful in diagnosis of pituitary tumors; however, MRI provides superior soft-tissue contrast as compared with CT and also is more accurate for visualization of smaller pituitary tumors. Treatment Medical therapy has been successful in some cats with HAC; however, the majority of cats do not respond to mitotane (Lysodren (o=p=-ddd) Bristol-Myers Squibb). 16 Trilostane is an orally administered competitive inhibitor of 3-betahydroxysteroid dehydrogenase, the enzyme that mediates the conversion of pregnenolone to progesterone and, hence, its end-products (cortisol, aldosterone, and androstenedione) in the adrenals. Studies in cats with HAC have shown that trilostane is an effective steroid inhibitor that is associated with minimal side effects Trilostane is administered at a dosage of 30 to 60 mg per cat per day. Trilostane therapy is monitored with weekly ACTH stimulation tests to obtain cortisol concentrations of 5 g/dl on the pre- and post- ACTH samples. Although currently unavailable in the United States, trilostane may prove to be a reasonable alternative to mitotane therapy for HAC in cats. Surgical Therapy Surgical treatment of feline HAC consists of unilateral or, more commonly, bilateral adrenalectomy The reader is referred to surgical texts for an explanation of the surgical procedure; however, medical management of the cat during the operative and postoperative period is essential for a good outcome. Before adrenalectomy, the cat should be regulated on trilostane until the skin lesions of HAC have resolved and DN, if present, is reasonably well controlled (no ketones). With bilateral adrenalectomy, glucocorticoid (10-20 mg methylprednisolone acetate, DepoMedrol IM) and mineralocorticoid (deoxycorticosterone acetate, 12.5 mg IM) supplementation should be initiated immediately before adrenalectomy and monthly thereafter for the rest of the cat s life. Complications following adrenalectomy include dehiscence, poor wound healing, Addisonian crises, and enlargement of the pituitary tumor, which may result in blindness or seizures (Nelson s syndrome). Response to bilateral adrenalectomy is usually good, with most cats having a resolution of clinical signs in 2 to 4 months. In approximately 50% of cases, DM resolves completely and in the other 50% insulin requirements are decreased dramatically. Transsphenoidal hypophysectomy for the treatment of feline PDH is a viable alternative to adrenalectomy; however, this procedure is not performed in the United States. 23 Radiation Therapy Because approximately 85% of cats with HAC have PDH, radiation therapy is another treatment option for many patients; however, radiation therapy is expensive ($1500 to $2000) and time-consuming (3 weeks duration). Radiation therapy is an effective method of treatment in cats associated with low morbidity, but signs of PDH may take several months to subside in treated animals. 24 The major advantage of pituitary irradiation is that the primary disorder, a pituitary tumor, has been addressed. Cats with FCS that undergo bilateral adrenalectomy followed by pituitary irradiation have the best prognosis and many will live a normal life (with resolution of the DM) following these procedures. 24 Feline Hyperaldosteronism Feline hyperaldosteronism may be caused by a unilateral aldosterone-secreting adrenal tumor or bilateral adrenal hyperplasia Tumors of the adrenal are usually benign; however, reports of an adrenocortical carcinoma secreting aldosterone have been described. 28 Oversecretion of aldosterone results in the classic electrolyte changes of hypokalemia, hypernatremia, and metabolic alkalosis (opposite of Addison s disease). However, primary hyperaldosteronism and secondary hyperaldosteronism caused by renal disease may be difficult to differentiate (Fig. 4). Hyperaldosteronism is associated with clinical signs resulting from systemic hypertension caused by expansion of blood volume or by polymyopathy resulting from hypokalemia. There is no breed predilection; however, reported cases tend to occur in older cats with a mean age of about 10 years and a range of 6 to 13 years. In a report of 13 cases of primary hyperaldosteronism in cats, the most common clinical sign was hypokalemic polymyopathy (n 13), presenting as ventroflexion of the neck (Fig. 5), in 11 cats, paresis in 3 cats, and hindlimb weakness in 3 cats. 26 Less commonly, hypertension (n 11), fundic changes (n 5; Fig. 6), blindness (n 2 cats), polydipsia and polyuria (n 3), and polyphagia (n 2) were observed. 26 Figure 4 Classification of primary versus secondary hyperaldosteronism.

14 Chicago Veterinary Medical Association - June 18, 2014 D. Chiaramonte and D.S. Greco 30 Figure 5 Cat with severe cervical ventroflexion from hypokalemia secondary to hyperaldosteronism. (Color version of figure is available online.) The most common laboratory findings were moderate to severe hypokalemia (mean, 2.5 mmol/l; range, ) in all 13 cats; elevations in serum creatine kinase was observed in 10 cats. Only one cat exhibited hypernatremia and no cats showed metabolic alkalosis (a characteristic of hyperaldosteronism in human beings).26 Also surprising was the low in- cidence of azotemia in these cats with only two cases showing elevations of both serum creatinine and BUN. Urine-specific gravity was normal in most of the cats; however, two cats did show isosthenuria. Elevated plasma aldosterone concentrations were measured in all 13 cases; the values ranged from 877 to 14,653 pmol/l with a mean value of 5820 pmol/l. Figure 6 Retinal hemorrhage in a cat with bilateral adrenal hyperplasia, high blood pressure ( 200 mm Hg), and evidence of primary hyperaldosteronism. (Color version of figure is available online.) Endocrinology with Deborah Greco DVM, PhD, DACVIM Page 13 of 60

15 Feline adrenal disorders 31 Plasma renin activity (PRA) was not measured in any of the cases. Abdominal ultrasonography revealed unilateral adrenal enlargement (1-3.5 cm) with an adrenal mass in 11/13 cases, all of which were biopsied and diagnosed as adrenal adenomas (seven cats) or carcinomas (six cats); two cats had bilateral adrenal enlargement with adenomas on postmortem examination. 26 Treatment of cats with primary hyperaldosteronism resulting from a unilateral adrenal tumor consists of potassium supplementation (Tumil K, 2-6 mmol PO), an aldosterone blocker such as spironlolactone (2.5 mg q 12 h PO), and amlodipine (0.125 mg q 24 h PO). None of the reported cases showed a normalization of serum potassium with supplementation; however, all cats showed resolution of the clinical signs of hypokalemia. 26 All but 2 of the 11 hypertensive cats became normotensive on calcium channel therapy. Three cats were treated medically and eventually euthanatized due to chronic progressive renal failure. Surgical removal of the adrenal mass has been considered the treatment of choice in most cases. 25,26,29 Eight cats were taken to surgery and five survived for 240 to 1803 days at the time of the article was written. 26 In cats with primary hyperaldosteronism caused by benign bilateral adrenal hyperplasia, hypertension, blindness, and renal failure are more common than signs of hypokalemia (ie, muscle weakness, cervical ventroflexion, paresis). 26,30 In a study of 11 cats with primary hyperaldosteronism, the cats were more likely to be older (range, years) and have higher systolic blood pressure ( mm Hg) than the cats with adrenal tumors. 30 Many of the affected cats exhibited ocular signs of hypertension such as retinal hemorrhage, hyphema, retinal detachments, and blindness (Fig. 6); in contrast, only two cats with adrenal tumors exhibited blindness as a clinical sign. Classic laboratory abnormalities observed in primary aldosteronism such as hypokalemia (6/11), elevated CK, and metabolic alkalosis are less commonly observed in cats with bilateral adrenal hyperplasia. 30 Hypernatremia was not observed in cats with bilateral adrenal hyperplasia. Azotemia was observed in 8 of the 11 cats. 30 In the case of bilateral adrenal hyperplasia, diagnosis was achieved by documentation of increased plasma aldosterone (N pmol/l), low to undetectable PRA, and/or increased plasma aldosterone concentration (PAC) to PRA ratios (PAC:PRA, normal ). In contrast to the previous study of adrenal tumors producing aldosterone, only four cats with bilateral adrenal hyperplasia had elevated PAC. 30 PRA was measured in all 11 cats in this study and was found to be abnormally low in 7 of the 11 cats. 30 However, all 11 cats showed a high PAC:PRA ratio (range, 4.0 to 41). Because idiopathic adrenal hyperplasia resulting in hyperaldosteronism is a bilateral disease, medical treatment is the only option available. Treatment of cats with primary hyperaldosteronism resulting from a bilateral adrenal hyperplasia consists of potassium supplementation (Tumil K, 2-6 mmol 2 PO), an aldosterone blocker such as spironlolactone(6.25 mg q 12 h PO), and antihypertensive therapy such as amlodipine (0.125 mg q 24 h PO) or beta-blockers (atenelol). Most of the cats with bilateral adrenal hyperplasia eventually succumb to progressive renal insufficiency. 30 References 1. Peterson ME, Steele P: Pituitary-dependent hyperadrenocorticism in a cat. J Am Vet Med Assoc 189(6): , Zerbe CA, Nachreiner RF, Dunstan RW, et al: Hyperadrenocorticism in a cat. J Am Vet Med Assoc 190(5): , Nelson RW, Feldman EC, Smith MC: Hyperadrenocorticism in cats: seven cases ( ). J Am Vet Med Assoc 193(2): , Immink WF: Four cats with Cushing s syndrome. Tijdschr Diergeneeskd 116:87S-88S, 1991 (suppl 1) 5. Rossmeisl JH Jr, Scott-Moncrieff JC, Siems J, et al: Hyperadrenocorticism and hyperprogesteronemia in a cat with an adrenocortical adenocarcinoma. J Am Anim Hosp Assoc 36(6): , Watson PJ, Herrtage ME: Hyperadrenocorticism in six cats. J Small Anim Pract 39(4): , Boord M, Griffin C: Progesterone secreting adrenal mass in a cat with clinical signs of hyperadrenocorticism. J Am Vet Med Assoc 214(5): , Schaer M, Ginn PE: Iatrogenic Cushing s syndrome and steroid hepatopathy in a cat. J Am Anim Hosp Assoc 35(1):48-51, Ferasin L: Iatrogenic hyperadrenocorticism in a cat following a short therapeutic course of methylprednisolone acetate. J Feline Med Surg 3(2):87-93, Nichols R: Complications and concurrent disease associated with diabetes mellitus. Semin Vet Med Surg (Small Anim) 12(4):263-7, Goossens MM, Meyer HP, Voorhout G, et al: Urinary excretion of glucocorticoids in the diagnosis of hyperadrenocorticism in cats. Domest Anim Endocrinol 12(4): , de Lange MS, Galac S, Trip MR, et al: High urinary corticoid/creatinine ratios in cats with hyperthyroidism. J Vet Intern Med 18(2): , Schoeman JP, Evans HJ, Childs D, et al: Cortisol response to two different doses of intravenous synthetic ACTH (tetracosactrin) in overweight cats. J Small Anim Pract 41(12): , Widmer WR, Guptill L: Imaging techniques for facilitating diagnosis of hyperadrenocorticism in dogs and cats. J Am Vet Med Assoc 206(12): , Mauldin GN, Burk RL: The use of diagnostic computerized tomography and radiation therapy in canine and feline hyperadrenocorticism. Probl Vet Med 2(4): , Moore LE, Biller DS, Olsen DE: Hyperadrenocorticism treated with metyrapone followed by bilateral adrenalectomy in a cat. J Am Vet Med Assoc 217(5): , 673, Skelly BJ, Petrus D, Nicholls PK: Use of trilostane for the treatment of pituitary-dependent hyperadrenocorticism in a cat. J Small Anim Pract 44(6): , Boag AK, Neiger R, Church DB: Trilostane treatment of bilateral adrenal enlargement and excessive sex steroid hormone production in a cat. J Small Anim Pract 45(5): , Neiger R, Witt AL, Noble A, et al: Trilostane therapy for treatment of pituitary-dependent hyperadrenocorticism in 5 cats. J Vet Intern Med 18(2): , Schwedes CS: Mitotane (o,p=-ddd) treatment in a cat with hyperadrenocorticism. J Small Anim Pract 38(11): , Duesberg CA, Nelson RW, Feldman EC, et al: Adrenalectomy for treatment of hyperadrenocorticism in cats: 10 cases ( ). J Am Vet Med Assoc 207(8): , Ivan Sluijs FJ, Sjollema BE: Adrenalectomy in 36 dogs and 2 cats with hyperadrenocorticism. Tijdschr Diergeneeskd 117:29S, 1992 (suppl 1) 23. Meij BP, Voorhout G, Van Den Ingh TS, et al: Transsphenoidal hypophysectomy for treatment of pituitary-dependent hyperadrenocorticism in 7 cats. Vet Surg 30(1):72-86, Mayer MN, Greco DS, LaRue SM: Outcomes of pituitary tumor irradiation in cats. J Vet Intern Med 20(5): , Flood SM, Randolph JF, Gelzer AR, et al: Primary hyperaldosteronism in two cats. J Am Anim Hosp Assoc 35(5): , Ahn A: Hyperaldosteronism in cats. Semin Vet Med Surg (Small Anim) 9(3): , DeClue AE, Breshears LA, Pardo ID, et al: Hyperaldosteronism and hyperprogesteronism in a cat with an adrenal cortical carcinoma. J Vet Intern Med 19(3): , Rijnberk A, Voorhout G, Kooistra HS, et al: Hyperaldosteronism in a cat with metastasised adrenocortical tumour. Vet Q 23(1):38-43, MacKay AD, Holt PE, Sparkes AH: Successful surgical treatment of a cat with primary aldosteronism. J Feline Med Surg 1(2): , Javadi S, Djajadiningrat-Laanen SC, Kooistra HS, et al: Primary hyperaldosteronism, a mediator of progressive renal disease in cats. Dom Anim Endocrinol 28:85-104, 2005

16 UPDATE ON THYROID DISORDERS Deborah S. Greco DVM, PhD, DACVIM Nestle Purina Petcare Congenital Hypothyroidism Congenital hypothyroidism, which occurs in approximately 1 in 4,000 births, is a relatively common endocrine disorder of human infants. In contrast, reports of congenital hypothyroidism in dogs and cats are relatively few. 1-8 Only 3.6% of the cases of canine hypothyroidism occur in dogs younger than 1 year of age. 4 However, spontaneous hypothyroidism is more common in the congenital form in cats. Congenital hypothyroidism may be caused by aplasia or hypoplasia of the thyroid gland, thyroid ectopia, dyshormonogenesis, maternal goitrogen ingestion, maternal radoactive iodine treatment, iodine deficiency (endemic goiter), auto-immune thyroiditis, hypopituitarism, isolated thyrotropin deficiency, hypothalamic disease, or isolated TRH deficiency. 2 Most cases of feline hypothyroidism in kittens have been the result of dysgensis; however, Jones et al reported a family of Abyssinian cats with familial dyshormonogenesis. 9 Hypothyroidism as a result of TSH resistance has also been described in a family of Japanese cats. 10 Most inherited forms of hypothyroidism are inherited as an autosomal recessive trait. Because thyroid hormone secretion is essential for normal post-natal development of the nervous and skeletal systems, congenital hypothyroidism is characterized by disproportionate dwarfism, central and peripheral nervous system abnormalities, and mental deficiency. (Figs 1 and 2) In addition, many of the signs of adult-onset hypothyroidism, such as lethargy, inappetence, constipation, dermatopathy, and hypothermia may be observed. 1-3 Congenital hypothyroidism, regardless of cause, results in characteristic historical and physical examination features. Kitten, puppies and infants have a history of large birth weight (in babies this is the result of prolonged gestation) which is followed by aberrant and delayed growth. 2,11 In puppies and kittens, the first signs of abnormal growth occur as early as 3 weeks after birth and abnormal body proportions are evident by 8 weeks of age. This is similar to human infants which are normal at birth but, if undiagnosed, exhibit characteristic signs by 6 to 8 weeks of age. 2 Historical findings in hypothyroid puppies and kittens, such as lethargy, mental dullness, weak nursing, delayed dental eruption and abdominal distension are also observed in hypothyroid children. 2 Physical features of hypothyroid dwarfism in children include hypotonia, umbilical hernia, skin mottling, large anterior and posterior fontanels, macroglossia, hoarse cry, distended abdomen, dry skin, jaundice, pallor, slow deep tendon reflex, delayed dental eruption and hypothermia. 2,12 In kittens and puppies with congenital hypothyroidism, hypotonia, macroglossia, distended abdomen, dry skin, delayed dental eruption and hypothermia have been described. 1-9 In addition, because dogs and cats develop more rapidly and become weight bearing sooner than human infants, gait abnormalities and disproportionate dwarfism are prominent features of canine congenital hypothyroidism. Midface hypoplasia, broad nose, and a large protruding tongue are some of the sequelae of untreated hypothyroidism in man. 13,14 Similar facial features, such as broad maxillas and macroglossia, have been observed in affected puppies and kittens. In man, delayed eruption of permanent teeth is observed in untreated congenitally hypothyroid individuals; 13 delayed dental eruption is characteristic of hypothyroid puppies and kittens treated after 4 months of age. In humans and in dogs and cats, both macroglossia and effusions of the body cavities are the result of myxedematous fluid accumulation. 15 Hypothyroid puppies and kittens often exhibit haircoat abnormalities including, retention of the puppy haircoat and thinning of the haircoat. Congenitally hypothyroid rats exhibit alterations in hair shaft morphology as a result of thyroid hormone deficiency during development. 16 Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 15 of 60

17 Thyroid hormone is crucial for proper post-natal development of the nervous system. As a result, a significant number of properly treated and all untreated hypothyroid infants exhibit poor coordination and speech impediments later in life. 17,18 Delayed treatment often results in low perceptual-motor, visual-spatial, and language scores in children with congenital hypothyroidism. 19 If treatment is delayed beyond 4 to 6 months in human babies, intelligence is irreversibly affected and mental retardation may ensue. 2 Mental retardation is also likely in hypothyroid puppies and kittens; however, no objective evidence of delayed intelligence is available to assess affected animals. Because the bulk of cerebellar development occurs post-natally, Purkinje cell growth is also significantly affected by congenital hypothyroidism. 19 In humans and puppies, if treatment is delayed, signs of cerebellar dysfunction, such as ataxia, are observed. Skeletal abnormalities such as delayed maturation and epiphyseal dysgenesis are the hallmark of congenital hypothyroidism. Delayed epiphyseal maturation is observed in the vertebral bodies and long bones of affected puppies and kittens. Epiphyseal dysgenesis, which is characterized by a ragged epiphysis with scattered foci of calcification, is observed in both humans and dogs with untreated congenital hypothyroidism. Normal epiphyseal development proceeds from a single center; however, in hypothyroidism, thyroid deficiency leads the development of multiple epiphyseal centers each with its own calcification progression. 20 Disorderly epiphyseal calcification leads to secondary arthropathies in children suffering from untreated congenital hypothyroidism. 20,21 Clinicopathologic features of congenital hypothyroidism include hypercholesterolemia, hypercalcemia, and mild anemia. Hypercholesterolemia develops in both congenital and adult-onset hypothyroidism because of decreased hepatic metabolism and decreased fecal excretion of cholesterol. Hypercalcemia secondary to congenital hypothyroidism is the result of decreased renal clearance and increased gastrointestinal absorption of calcium. 22,23 Decreased thyroid hormone stimulation of erythropoetic precursors results in a mild normocytic, normochromic anemia in some puppies and kittens suffering from hypothyroidism Thyroxine is essential for the proper transcription, translation and secretion of growth hormone by pituitary somatotrophs. 27 In man (and most likely the dog and cat), circulating GH concentrations are very high during the first few days after birth but rapidly decrease during the subsequent few weeks to levels just slightly above those in adults. 2 In a previously reported case of congenital hypothyroidism, the dog exhibited a blunted GH response to xylazine but had a normal GH response to provocative stimulation following treatment of the hypothyroid state. 7 Diagnosis of congenital hypothyroidism is based on clinical signs, supporting clinicopathology and thyroid function testing. Puppies exhibit serum TT4 concentration 2 to 5 times greater than adult dogs. It is vital to remember that normal puppies aged 5-6 weeks, have serum total thyroxine (TT4) concentrations 2-3 times higher than normal adult dogs. Therefore, a serum TT4 of 2.0 µg/dl, which is normal for an adult dog, would be low in a 6 week old puppy and indicative of thyroid dysfunction. Serum free thyroxine (FT4) would also be expected to be higher in neonatal dogs. In summary, congenital hypothyroidism is recognized by characteristic physical examination findings (dwarfism, delayed dental eruption, etc), clinicopathologic and radiological features and confirmed by thyroid function testing. Some authors have suggested that hypothyroidism may be a cause of neonatal mortality in puppies. Given the incidence of hypothyroidism in humans, it seems reasonable to screen neonatal puppies (1-5 weeks) in high-risk breeds for congenital hypothyroidism. Diagnosis of hypothyroidism in cats and dogs is based on measurement of serum basal total thyroxine (T4) and triiodothyronine (T3) concentrations, serum free T4 and T3 concentrations, antithyroglobulin autoantibodies, endogenous canine serum TSH levels and response to therapy. Often, the combination of basal TT4 and endogenous TSH concentrations is the most economical and efficient way to diagnose hypothyroidism in dogs (or cats). Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 16 of 60

18 References 1. Greco DS, Peterson ME, Cho DY. Juvenile-onset hypothyroidism in a dog. J Am Vet Med Assoc 187: , LaFranchi SH. Hypothyroidism. Pediatr Clin North Am 26:33-51, Feldman EC, Nelson RW. Canine and Feline Endocrinology and Reproduction, 3rd ed. Philadelphia: WB Saunders, Milne Kl, Hayes HM. Epidemiologic features of canine hypothyroidism. Cornell Vet 71:3-14, Chastain CB, McNeil SV, Graham CL, et al. Congenital hypothyroidism in a dog due to an iodide organification defect. Am J Vet Res 44: , Rijnberk A. Iodine metabolism and thyroid disease in the dog, PhD thesis. University of Utrecht, The Netherlands, Medleau L, Eigenmann JE, Saunders HM, et al. Congenital hypothyroidism in a dog. J Amer Anim Hosp Assoc 21: , Robinson WF, Shaw SE, Stanley B, et al. Congenital hypothyroidism in Scottish Deerhound puppies. Aust Vet J 65: , Jones BR, Gruffydd-Jones TJ Sparkes AH et al. Preliminary studies on congenital hypothyroidism in a family of Abyssinian cats. Vet Record, 131: , Tanase H, Kudo K, HorikoshiH, et al. Inherited primary hypothyroidism with thyrotrophin resistance in Japanese cats. J Endocrinol 129: , Kenny FM, Klein AH, Augustin AV, et al. Sporadic cretinism, in Fisher DA, Gurrow GN, eds. Perinatal thyroid physiology and disease. New York Raven Press, 1975, pp Fisher DA. Medical management of suspected cases of congenital hypothyroidism. In: Neonatal thyroid screening. Burrow GN (ed). New York: Raven Press, 1980, pp Loevy HT, Aduss H, Rosenthal IM. Tooth eruption and craniofacial development in congenital hypothyroidism: report a of case. J Am Dent Assoc 115: , Isreal H, Johnson GF, Fierro-Benitez R. Craniofacial malformation among endemic cretins in Ecuador. J Craniofac Genet Dev Biol 3: 3-10, Sawin CT. Hypothyroidism. Med Clin N Amer 69: , Essman EJ. Alterations in hair shaft morphology in the cretin rat. Bio Clin Lab 14: , Moschini L, Costa P, Marinelli E, et al. Longitudinal assessment of children with congenital hypothyroidism detected by neonatal screening. Helv Paediatr Acta 41: , Noguchi T, Sugisaki T. Hypomyelination in the cerebrum of the congenitally hypothyroid mouse (hyt). J Neurochem 42: , Rovet J, Ehrlich R, Sorbara D. Intellectual outcome in children with fetal hypothyroidism. J Pediatr 10: , Wilkins L. Epiphyseal dysgenesis associated with hypothyroidism. Am J Dis Child 61:13-34, Johansen NA. Endocrine arthropathies. Clin Rheum Dis 11: , Parfitt AM, Kleerekoper M. Clinical disorders of calcium, phosphorus, and magnesium metabolism. In: Maxwell M, Kleeman CR, eds. Clinical disorders of fluid and electrolyte metabolism. New York: McGraw-Hill Book Co, 1980; pp Tau C, Garagedian M, Farriaux JP, et al. Hypercalcemia in infants with congenital hypothyroidism and its relation to vitamin D and thyroid hormones. J Pediatr 109: , Cline MJ, Berlin NI. Erythropoesis and red cell survivial in the hypothyroid dog. Am J Physiol 204: , Schalm OW, Jain NC, Carroll EJ. Veterinary Hematology, 3rd ed. Philadelphia: Lea & Febiger, 1975, pp DeGroot LJ, Larsen PR, Hennemann G. The thyroid and its diseases, 6 th ed. Churchill Livingstone, 1996,pp Wood DF, Franklyn JA, Docherty K. The effect of thyroid hormones on growth hormone gene expression in vivo in rats. J Endocrinol 112: , Casal ML, Zerbe, CA, Jezyk PF, Refsal KR, Nachreiner RF. Thyroid profiles in healthy puppies from birth to 12 weeks of age. Proc Amer Coll Vet Int Med, 1994, San Francisco CA, p Graham PA, Refsal KR, Nachreiner RF, et al. The measurement of feline thyrotropin using a commercial canine immunoradiometric assay. J Vet Int Med 2000:14:342. Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 17 of 60

19 UPDATE ON THE PATHOGENESIS OF FELINE HYPERTHYROIDISM Deborah S. Greco DVM, PhD, DACVIM Nestle Purina Petcare Feline hyperthyroidism was first described in 1979 and 1980 by investigators in NYC and Boston. (Peterson 1979, Holzworth 1980) The question at that time and since then has been: Is hyperthyroidism a new disease in cats? Based on epidemiologic and hospital-acquired data, the answer appears to be yes. During a 14 year period from , an average of 1.9 cats per year were diagnosed with hyperthyroidism; however, it is now estimated that the incidence is as high as 2% of the feline population seen in tertiary care veterinary facilities. (Peterson 1994, Edinboro 2004) Since then, hyperthyroidism has become the most frequently diagnosed endocrinopathy in the cat with reports stemming from North America, Europe (esp UK), New Zealand and Australia. Hyperthyroidism in cats has become increasingly more prevalent due to an increase in the number of cats that survive past 10 years of age, because of improved diagnostics and because of increased suspicion for the disease among veterinarians in practice. Dozens of studies have been published on the origins of feline hyperthyroidism; however, none provide a definitive answer to the mystery behind this disease. Nutritional aspects of hyperthyroidism Canned cat food has been implicated as a cause of feline hyperthyroidism in multiple epidemiological studies. (Kass 1999, Martin 2000, Edinboro 2004) The suspected goitrogen is bisphenol-a-diglycidyl ether (BADGE), a substance used in making the liner of easy-open pop-top cans. It is suspected that this compound can leach into the foods and be consumed by cats. While this BADGE-based lining is generally considered safe and is used for foods for human consumption, cats may be more susceptible to toxic effects of this compound because they have a greatly reduced ability to detoxify it via hepatic glucuronidation Bisphenol A also reduces triiodothyronine binding and causes increased TSH secretion resulting in hyperthyroidism and goiter in rats and some humans. While cat studies may not be available, rodent studies show a very high safety margin. (Poole 2004) It should be noted that epidemiological studies showing associations are not the same as cause and effect. Over 90% of cats in the US consume commercial pet foods as their primary nutritional source, and relatively few develop hyperthyroidism Molecular aspects of hyperthyroidism More recently, investigators have honed in on the molecular aspects of feline hyperthyroidism. The disease in cats is more similar to toxic nodular goiter in humans and is characterized by autonomous growth of thyroid follicles. The pathogenesis of toxic nodular goiter is an abnormality in the signal transduction of the thyroid cell. The TSH receptor on the thyroid cells activated receptor-coupled guanosine triphosphate-binding proteins (G proteins). Uniquely, the thyroid cell proliferation and hormone production are both controlled by the TSH receptor-g-protein-camp signaling. Overexpression of stimulatory G proteins and underexpression of inhibitory G proteins have been demonstrated in some humans with toxic nodular goiter. (Derwalht 1995, Delmer 1992) Mutations of the TSH receptor that result in the receptor remaining activated without ligand (ie, TSH) have also been reported in humans with toxic nodular goiter. (Parma 1997, Fuhrer 1997, Holzapfel 1997, Russo 1996) In hyperthyroid cats, the same abnormalities have been investigated and it appears that activation mutation of the TSH receptor may be part of the pathogenesis of feline hyperthyroidism in some cats. (Peeters 2002) Furthermore, abnormalities of G proteins, specifically significantly decreased G inhibitory protein expression has been described in tissues from hyperthyroid cats. (Hammer 2000) Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 18 of 60

20 Environmental aspects of hyperthyroidism In one study, the use of cat litter was associated with an increased risk of hyperthyroidism (Kass 1999); however, there was no significant difference between different litter brands suggesting that the use of litter is simply a marker of cats that are kept indoors. (Peterson and Ward 2007) Indoor cats are likely to live longer and hence have a higher risk of developing hyperthyroidism. Exposure to pesticides and herbicides has been associated with thyroid abnormalities in other species. (Gaitan 1990) In particular, the use of flea control products was associated with an increased risk of developing hyperthyroidism; however, no specific product or ingredient could be identified. (Scarlett 1988, Olkzak 2005) One recent report implicated brominated flame retardants (BFRs) as carcinogens/goitrogens possibly associated with feline hyperthyroidism.(dye 20007) Coincidently BFRs were introduced 30 years ago at the same time that feline hyperthyroidism emerged. Bromide, a halide, is an intriguing agent to implicate in feline hyperthyroidism because of the unique composition of thyroid hormones which contain the halide iodide. In this recent abstract, serum levels of lipid adjusted serum polybrominated diphenyl ethers (PBDE) levels were fold higher than those found in human exposure The authors theorized that these findings of high PBDE serum levels is in accord with the most consistently identified risk factor which is indoor living. The authors also propose that cats are at increased risk because of meticulous grooming behavior and increased exposure to furniture and carpets. The small size of cats is also a possible risk factor for increased serum levels of PBDEs. References 1. Brown et al. Thyroid growth immunoglobulins in feline hyperthyroidism. Thyroid 1992;2: Delemer B, Dib K, Patey m, et al. Modification of the amounts of G proteins and of the activity of adenyl cyclase in human benign thyroid tumours. J Endocrinol 1992; Derwahl M, Hamacher C, Papageorgiou G. Alterations of the stimulatory G protein (Gs)-adenylate cyclase cascade in thyroid carcinomas: evidence for up regulation of inhibitory G protein. Thyroid 1995; 5 (Suppl 1): S Dye JA, Venier M, Ward CA. Brominated-flame retardants (BFRs) in cats-possible linkage to feline hyperthyroidism. (abstract) J Vet Int Med May 2007; p Edinboro CH, Scott-Moncrieff JC, Janovitz E, et al. Epidemiologic study of relationship between consumption of commercial canned food and risk of hyperthyroidism in cats. J Am Vet Med Assoc 2004;224: Fuhrer D, Holzapfel Hp, Wonerow P, et al. Somatic mutations in the thyrotropin receptor gene and not in the Gs alpha protein gene in 31 toxic thyroid nodules. J clin Endocrinol Metab 1997; 82: Hammer KB, Holt DE, Ward CR. Altered expression of G proteins in thyroid gland adenomas obtained from hyperthyroid cats.am J Vet Res 2000;61: Holzworth J, Theran P, Carpenter JL, et al. Hyperthyroidism in the cat: ten cases. J Am Vet Med Assoc 1980;176: Kang JH, Kondo F. Determination of bisphenol A in canned pet foods. Res Vet Sci 2002;73: Kass PH, Peterson ME, Levy J, et al. Evaluation of environmental, nutritional and host factors for feline hyperthyroidism. J Vet Intern Med 1999; 13: Martin KM, Rossing MA, Ryland LM. Evaluation of dietary and environmental risk factors for feline hyperthyroidism. J Am Vet Med Assoc 2000; 217: Mooney CT. Pathogenesis of hyperthyroidism. J Vet Med Surg 2002; 4: Moriyama K, Tagami T, Akimizu T, et al. Thyroid hormone action is disrupted by bisphenol A as an antagonist. J Clin EndocrinolMetab 2002;87: Nguyen LQ, Arseven RK, Gerber H, et al. Cloning of the cat TSH receptor and evidence against an autoimmune etiology of feline hyperthyroidism. Endocrinology 2002;143: Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 19 of 60

21 15. Olczak J, Jones BR, Pfeiffer DU, et al. Multivariate analysis of risk factors for feline hyperthyroidism in New Zealand. N Z Vet J 2005; 53: Parma J, Duprez L, Van Sande J, et al. Diversity and prevalence of somatic mutations in the thyrotropin receptor and Gs alpha genes as a cause of toxic thyroid adenomas. J Clin Endocrinol metab 1997:82: Peeters ME, Timmermans-Sprang EP, Mol JA. Feline thyroid adenomas are in part associated with mutations in the G (s alpha) gene and not with polymorphisms found in the thyrotropin receptor. Thyroid 2002; 12: Peterson ME, Johnson JG, Andrews LK. Spontaneous hyperthyroidism in the cat. In Scientific Proc Amer College Vet Int Med 1979, p Peterson ME, Kintzer PP, Cavanaugh PG, et al Feline hyperthyroidism: pretreatment clinical and laboratory evaluation of 131 cases. J Am Vet med Assoc 1981;183: Peterson ME, Ward C. Etiopathologic findings of hyperthyroidism in cats. Vet Clin N Amer Sm Anim Pract 2007, in press. 21. Poole A, van Herwijnen P, Weideli H, et al. Review of the toxicology, human exposure and safety assessment for bisphenol A diglycidylether (BADGE). Food Addit Contam 2004; 21(9): Russo D, Arturi F, Suarez HG, et al. Thyrotropin receptor gene alterations in thyroid hyperfunctioning adenomas. J Clin Endocrinol Metab 1996;81: Scarlett JM, Moise NS, Ravl J. Feline hyperthyroidism: goitrogens descriptive and case controlled study. Prev Vet Med 1988; 6: Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 20 of 60

22 CANINE DIABETES MELLITUS AND DIABETIC KETOACIDOSIS Deborah S. Greco DVM, PhD, Diplomate ACVIM Nestle Purina PetCare ETIOLOGY Insulin dependent diabetes mellitus (IDDM) is a diabetic state in which endogenous insulin secretion is never sufficient to prevent ketone production. Type I diabetes mellitus is a diabetic state in which insulin secretion may be reduced or absent and which is readily corrected by exogenous insulin; in dogs, Type Ia diabetes is caused by autoimmune destruction of the beta cells (genetic disorder related to hypothyroidism) and Type Ib (mature onset diabetes of the young) which is a non-immune destruction of islets caused by pancreatitis or an unknown cause. KEY POINT: Most dogs suffer from Type I diabetes or IDDM. Type III or secondary diabetes mellitus is the result of another primary disease or drug therapy producing insulin resistance (hyperadrenocorticism, hyperthyroidism, acromegaly, progestational drugs) or destroying pancreatic tissue (pancreatitis). Secondary diabetes is common in both dogs (pancreatitis, endocrinopathies) and cats (drugs, endocrinopathies, pancreatitis). In animals with uncomplicated diabetes mellitus, hyperglycemia results from impaired glucose utilization, increased gluconeogenesis and increased hepatic glycogenolysis. Decreased peripheral utilization of glucose leads to accumulation of glucose in the serum followed by osmotic diuresis. Progressive dehydration causes the classic clinical signs of polyuria with compensatory polydipsia. Impaired glucose utilization by the hypothalamic satiety center combined with loss of calories in the form of glycosuria results in the clinical signs of polyphagia and weight loss, respectively. Insulin is anabolic; therefore, insulin deficiency leads to protein catabolism and contributes to the clinical signs of weight loss and muscle atrophy. As a consequence of protein catabolism, amino acids such as alanine are utilized by the liver to promote gluconeogenesis and contribute to hyperglycemia. With insulin deficiency, the hormone-sensitive lipase system which is normally suppressed by insulin becomes activated. The unrestrained lipolytic activity of hormone sensitive lipase results in the clinical signs of weight loss in a previously obese or overweight animal. CLINICAL SIGNS OF NON-KETOTIC DIABETES MELLITUS Dogs suffering from diabetes mellitus range in age from 4-14 years with a peak incidence at 7-9 years. A genetic basis for diabetes mellitus is suspected in the keeshonden. Other commonly affected breeds include miniature and toy poodles, dachshunds, miniature schnauzers, beagles, puliks, Cairn terriers and miniature pinschers. In dogs, females are twice as likely to develop diabetes as males. Most diabetic animals present with the classic clinical signs of polyuria and polydipsia. Weight loss is commonly observed in dogs. In some cases, polyphagia is also observed. In dogs, progressive polyuria, polydipsia and weight loss develops relatively rapidly usually over a period of several weeks. Another common presenting complaint of diabetes mellitus in dogs is acute onset of blindness caused by bilateral cataract formation. Physical Examination Findings Physical examination findings of non-ketotic diabetes mellitus in dogs are typically non-specific. In dogs, the most common physical examination findings are dehydration and muscle wasting or thin body condition. About Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 21 of 60

23 25-30% of diabetic animals are obese upon initial examination. Hepatomegaly isusually observed in diabetic dogs. Cataracts are observed in approximately 40% of diabetic dogs. Clinical Pathology A diagnosis of diabetes mellitus should be based on the presence of clinical signs compatible with diabetes mellitus and evidence of fasting hyperglycemia and glycosuria. Common clinicopathologic features of diabetes mellitus in dogs include: fasting hyperglycemia hypercholesterolemia, increased liver enzymes (ALP, ALT), neutrophilic leukocytosis, proteinuria, increased urine specific gravity and glycosuria. TREATMENT Insulin Therapy Human recombinant insulin is the most available insulin preparation on the market and is perfectly acceptable as insulin therapy for all dogs. Porcine insulin is identical to canine insulin in its amino acid structure and human insulin is very similar to canine insulin. Insulin preparations may be short-acting (regular insulin), intermediate (Lente, NPH) or long-acting (Ultralente, PZI). NPH and PZI insulin is made from regular insulin by adding protamine in increasing concentrations to retard insulin absorption. Protamine zinc insulin (PZI) was discontinued as a human preparation in 1991 and has just recently become available again to veterinarians as a U-40 insulin (Blue Ridge Pharmaceuticals). Lente preparations control absorption by regulating the size and shape of the insulin crystals. Semilente is composed of small, amorphous zinc-insulin, and ultralente is composed of large zinc-insulin crystals which are more slowly absorbed. Lente insulin is a mixture of 30% prompt zinc-insulin suspension (semilente) and 70% extended insulin zinc (Ultralente). Lente insulin, because of the small zinc-insulin crystal component, may be used to attenuate postprandial hyperglycemia. Glargine (Lantus) insulin is a human recombinant insulin which has substituted amino acids and an acid ph which causes precipitation at injection; the starting dose is 0.5 U/kg. Detomir (Levomir) insulin is a human recombinant (yeast) insulin in which a fatty acid has been substituted for an AA; it is highly protein bound (lipid soluble) and the dose is U/kg BID in dogs. Insulin concentration Insulin is commercially available in 40, 100, and 500 U/ml concentrations which are designated U-40, U-100, and U-500 respectively. One unit of insulin is approximately equivalent to 36 µg. Regardless of the concentration of insulin used for therapy, it is absolutely essential that owners purchase the appropriate syringe for the concentration of insulin. PZI insulin is manufactured as U-40 concentration only. U-100 insulin syringes are manufactured as low-dose (0.3 ml, 0.5 ml), and 1 ml capacities; U-40 syringes are only available as 1 ml capacity. All insulin syringes are packaged with a fine 26 or 27 gauge injection needle. In small dogs (<10 kg), the use of low-dose (0.3 or 0.5 ml) syringes is recommended. These syringes are designed to accurately draw up a small dosage of U-100 insulin without the need for dilution. Insulin Dosage Intermediate-acting insulin tends to be more bioavailable and therefore, more potent and is most appropriately dosed at the lower end of the range. Therefore, intermediate-acting insulin (NPH, Lente, glargine) is administered twice daily, at a starting dosage of U/kg in dogs. Long acting insulins, such as PZI, are dosed once daily at U/kg. Detemir insulin is dosed at ( U/kg) BID in dogs. Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 22 of 60

24 Insulin: Frequency of Dosing In order to mimic the physiologic release of insulin, ideally insulin should be given with each meal. The author recommends feeding the animal and injecting the insulin at the same time. If the animal does not eat, the insulin dosage can be reduced (usually by one-half) or skipped entirely and the animal evaluated by the veterinarian to determine the cause of the anorexia. Adjustments to Insulin Dosage at Home In general, the client should be instructed to monitor the insulin effect and gross regulation of hyperglycemia by noting changes in appetite, attitude, body condition, polydipsia, polyuria and urine glucose and ketone levels. Consistently high urine glucose readings coupled with uncontrolled clinical signs, such as PU/PD, indicate that the insulin dose may be inadequate. Consistently negative readings on urine glucose may indicate that insulin dosages are either adequate or excessive. A serial glucose curve is required to differentiate between adequate insulin therapy and excessive therapy that could result in hypoglycemic shock. Insulin Injection Location and Technique The author recommends administration of insulin at sites along the lateral abdomen and thorax. Clipping or shaving a 2 x 2 square of haired skin on the lateral thorax or abdomen will assist the owner in accurate insulin placement. It often helps to reinforce verbal instructions with written comments that the owner can refer to if they cannot recall the veterinarian's exact instructions. The owner should be instructed to draw up the insulin using the appropriate insulin syringe. The insulin bottle is first removed from the refrigerator and warmed to room temperature by gentle rolling or agitation. The insulin bottle is turned upside down and the appropriate number of units drawn into the syringe. A common mistake that owners may make is to measure the insulin dosage by the bottom rather than the top of the plunger. The owner should be observed drawing up saline to determine if accurate insulin dosage is being measured. After the insulin is drawn up in the syringe, the client should be instructed to inject the insulin by lifting the loose skin over the abdomen or thorax and inserting the needle into the skin at a 45 degree angle and parallel to the long axis of the skin fold. If the needle is inserted perpendicular to the skin fold, the needle may penetrate the other side of the skin fold and the insulin will be deposited on the hair. DIET and EXERCISE The goals of dietary therapy in diabetes mellitus for both cats and dogs are to provide sufficient calories to maintain ideal body weight and correct obesity or emaciation, to minimize post-prandial hyperglycemia, and to facilitate ideal absorption of glucose by timing meals to coincide with insulin administration. Caloric intake should be Kcal/kg/day for smaller dogs and Kcal/kg/day for larger dogs. Obese animals should have their body weight reduced gradually over a period of 2-4 months by feeding 60-70% of the calculated caloric requirements for ideal body weight. Underweight animals should be fed a high-caloric density food based on caloric intake for optimum body weight. Once ideal body weight is reached, the animal may be switched to a high fiber diet. Table 2 lists the fiber and caloric content of some commercially available dog foods. The feeding schedule should be adjusted to the insulin therapy. Micronutrients may be added to the diet to improve glucose control in some dogs. Compounds containing the transition metals, vanadium and chromium, have been shown to have insulinomimetic properties when administered to diabetic rodents. A recent USDA study of 180 human patients with NIDDM found that administration of 1,000 µg of chromium picolinate once daily resulted in amelioration of the classic signs of Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 23 of 60

25 diabetes and normalization of blood levels of hemoglobin A1c. Current research indicates that transition metals bypass the insulin-receptor and activate glucose metabolism within the cell. Unlike insulin, vanadium and chromium do not lower blood glucose concentrations in normal animals. One of the newer approaches to managing diabetes mellitus in dogs combines the use of nutritional components such as starch blends, carboymethyl cellulose and fermentable fiber blends. Barley and sorghum are used to blunt the post-prandial rise in blood glucose, adjust postprandial insulin to appropriate levels, and to help blunt glucose surge. Fermentable fibers, such as FOS, beet pulp and gum arabic, increase short chain fatty acids from the large intestine which in turn increases glucogon like peptide-1 secretion and activity. GLP-1 is necessary for normal insulin secretion and for normal timing of insulin secretion after eating. L-carnitine is used to promote weight loss in overweight diabetic dogs and carboymethylcellulose delays gastric emptying further blunting the glucose surge that occurs after feeding. Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 24 of 60

26 Diabetic Ketoacidosis and Hyperosmolar Nonketotic Diabetes Mellitus Deborah S. Greco, DVM, PhD, DACVIM Nestle Purina Petcare Abstract Diabetic ketoacidosis and hyperosmolar nonketotic diabetes mellitus are life-threatening metabolic emergencies in dogs and cats with poorly controlled or undiagnosed diabetes mellitus or diabetic patients with other concurrent conditions, sch as pancreatitis. Acute management of the ketoacidotic patient including fluid therapy, insulin therapy, and electrolyte supplementation to reverse metabolic acidosis is discussed in detail in this article. Treatment of hyperosmolar nonketotic diabetes mellitus, a less common condition, is similar but on a much slower time scale, and the prognosis is poor. Key Facts Diabetic ketoacidosis (DKA) is the culmination of diabetes mellitus that results in unrestrained ketone body formation in the liver, metabolic acidosis, severe dehydration, shock, and possibly death. In hyperosmolar nonketotic diabetic mellitus, some beta cells are still functioning and producing insulin, preventing the formation of ketones. It is defined by extreme hyperglycemia, hyperosmolality, severe dehydration, central nervous system depression, no ketone body formation, and absent or mild metabolic acidosis. Diagnostics/lab findings The most important part of urinalysis is measurement of glucose and ketones. A strongly positive glucose confirms diabetes mellitus and a positive result for ketones confirms DKA. A negative ketone result, however, does not definitively rule out ketosis. Although serum potassium may be high or in the normal range at presentation, patients with DKA have total body depletion of potassium. In addition, serum potassium concentrations will plummet following insulin therapy as a result of insulin-facilitated intracellular potassium exchange. Treatment Treatment of diabetic ketoacidosis includes the following steps in order of importance: 1) fluid therapy using 0.9% saline initially, followed by 2.5% or 5% dextrose as serum glucose falls; 2) insulin therapy (low-dose intramuscular or intravenous); 3) electrolyte supplementation (potassium, phosphorus, magnesium); and 4) reversal of metabolic acidosis. In HONKDM, fluid therapy should be judicious and designed to slowly replace maintenance and dehydration deficits. Correct fluid and electrolyte imbalances very slowly. The goal should be to correct dehydration over 36 hours Hyperosmolar nonketotic diabetic mellitus requires similar treatment to DKA but on a much slower time scale. Insulin therapy may be delayed for 24 hrs to allow slow rehydration of cerebral tissues The prognosis for diabetic ketoacidosis in dogs is fair to good as long as the underlying disorder is treatable (eg, urinary tract infection, pneumonia). With acute pancreatitis, the prognosis depends on the severity of the Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 25 of 60

27 pancreatic disease in both dogs and cats. Cats with hyperosmolar nonketotic or mixed ketotic syndrome have a very poor prognosis. Diabetic ketoacidosis (DKA) is the culmination of diabetes mellitus that results in unrestrained ketone body formation in the liver, metabolic acidosis, severe dehydration, shock, and possibly death. Hepatic lipid metabolism becomes deranged with insulin deficiency and nonesterified fatty acids are converted to acetyl-coenzyme A (acetyl-coa) rather than being incorporated into triglycerides. Acetyl-CoA accumulates in the liver and is converted into acetoacetyl-coa and then ultimately to ketones including acetoacetic acid, betahydroxybutyrate (primary ketone in dogs and cats), and acetone. As insulin deficiency culminates in DKA, accumulation of ketones and lactic acid in the blood and loss of electrolytes and water in the urine results in profound dehydration, hypovolemia, metabolic acidosis, and shock. Ketonuria and osmotic diuresis caused by glycosuria causes sodium and potassium loss in the urine exacerbating hypovolemia and dehydration. Nausea, anorexia, and vomiting, caused by stimulation of the chemoreceptor trigger zone via ketonemia and hyperglycemia, contribute to the dehydration caused by osmotic diuresis. Dehydration leads to further accumulation of glucose and ketones in the blood. Stress hormones such as cortisol and epinephrine contribute to the hyperglycemia in a vicious cycle. Eventually severe dehydration may result in hyperviscosity, thromboembolism, severe metabolic acidosis, renal failure, and finally death. Hyperosmolar nonketotic diabetic mellitus (HONKDM) is a less common complication of DM. It has a similar pathogenesis to DKA with a relative deficiency in insulin. For the hyperosmolar syndrome to develop, some functioning beta cells must still be producing insulin. The existence of some insulin prevents the formation of ketones. Excessive dehydration leads to a decrease in glomerular filtration rate (GFR), which leads to a decrease in glucose excretion. Hyperglycemia worsens and causes an increase in plasma osmolality. Increased plasma osmolality draws water out of cerebral neurons resulting in obtundation and decreased water intake, which ends in a vicious cycle. Historical Findings Most dogs and cats with DKA present with a previous history of uncomplicated diabetes including polyuria and polydipsia and dramatic and rapid weight loss in the face of a good or even ravenous appetite (Figure 2). Additional more recent historical findings include anorexia, weakness, depression, vomiting, and diarrhea. Occasionally owners fail to notice the significance of the classical signs of diabetes mellitus and the animals are presented solely with an acute history of DKA. It is also possible for DKA to develop in previously well-controlled, treated diabetic patients. Patients with hyperosmolar nonketotic diabetic mellitus typically are quite depressed. They may be comatose upon presentation. The history of weakness may be for several weeks prior to presentation. Physical Examination Findings The most common physical examination findings in DKA are lethargy and depression, dehydration, unkempt haircoat, and muscle wasting. Hepatomegaly is common in both diabetic cats and dogs. Cataracts are commonly observed in diabetic dogs. A plantigrade rear limb stance resulting from diabetic neuropathy is often observed in diabetic cats. Other findings include tachypnea, dehydration, weakness, vomiting, and occasionally, a strong acetone odor on the breath. Cats can present recumbent or comatose and this may be a manifestation of mixed ketotic hyperosmolar syndrome (Figure 3). Icterus can develop as a result of the complicating factors of hemolysis, hepatic lipidosis, or acute pancreatitis. Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 26 of 60

28 Laboratory Findings The average blood glucose in patients with DKA is 25 mmol/l. Values can range from 10 to more than 50 mmol/l, but the latter is more characteristic of hyperosmolar coma (1). Although portable glucose meters are commonly used to monitor glucose concentrations in DKA, caution is advised in relying on these monitors for baseline glucose concentrations because of inaccuracies in the face of severe hyperglycemia. All DKA patients have a relative or absolute deficiency of insulin and excessive hepatic production of glucose resulting in hyperglycemia. Hyperglycemia is further exacerbated by dehydration and the corresponding reduction in glomerular filtration rate (GFR) and these factors are important determinants of its severity. This is supported by the findings that glucose concentrations exceed 25 mmol/l only when dehydration is severe enough to reduce GFR and thus the ability of the kidneys to excrete glucose, and that fluid administration alone can significantly reduce blood glucose concentrations (2). Osmolality is usually mildly to markedly increased in the DKA patient as a result of hyperglycemia, but may not be detected, in part because of concurrent hyponatremia (3,4) Sodium and to a lesser extent, potassium, glucose, and urea concentrations are the determinants of the calculated serum osmolality. Reference values for serum osmolality in dogs and cats are approximately 290 to 310 mosm/kg. Hyperosmolality is generally mild enough to resolve with intravenous fluid and insulin therapies. Nonketotic hyperosmolar diabetes is defined by extreme hyperglycemia (>30 mmol/l, 600 mg/dl), hyperosmolality (> 350 mosm/l), severe dehydration, central nervous system (CNS) depression, no ketone body formation, and absent or mild metabolic acidosis (5). Affected patients are more likely to have underlying renal or cardiovascular disease and are more likely to be non-insulin-dependent (4). Although this specific syndrome, as defined in humans, is uncommonly encountered in veterinary medicine, it is not uncommon to have ketotic or nonketotic diabetic cats with significant hyperosmolality and CNS alterations (6). Most patients suffering from DKA have a total body potassium deficit due to urinary (osmotic diuresis), anorexia, and gastrointestinal (vomiting and anorexia) losses. The metabolic acidosis, relative or absolute insulin deficiency, and serum hypertonicity combine to cause a shift of potassium from the intracellular to the extracellular compartment. This is capable of masking the severity of total body hypokalemia when plasma concentrations are measured. Insulin therapy, as well as correction of the acid-base disturbance with fluids and/or bicarbonate will drive serum potassium intracellularly, potentially causing marked circulating hypokalemia (7). Polyuric patients are predisposed to severe hypokalemia, while oliguric or anuric patients are predisposed to severe hyperkalemia. In general, DKA causes significant total body sodium deficits. Excessive urinary loss of sodium results from the osmotic diuresis induced by high glucose and ketone concentrations and the lack of insulin, which usually aids in reabsorption of sodium from the distal nephron. Hyperglucagonemia, vomiting, and diarrhea also contribute to the total body sodium loss. Hyperosmolality may contribute to a low sodium concentration because as osmolality increases, water is drawn from the interstitium into the vascular space, thus diluting plasma sodium and chloride. Phosphorus is the major intracellular anion and is important for energy production and for maintenance of cell membranes. Concentrations are regulated by dietary intake, renal elimination, factors promoting its movement into and out of cells, and vitamin D and parathyroid interactions. In DKA, circulating concentrations are usually within reference range or increased initially because of dehydration and/or renal disease. Phosphorus may also be low at presentation because of urinary loss due to osmotic dieresis (8). As long as renal function is not Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 27 of 60

29 compromised, a significant decrease in phosphorus should be anticipated with therapy. Following insulin administration, phosphorus shifts to the intracellular compartment with glucose. Clinical signs of hypophosphatemia such as hemolytic anemia (also seen with Heinz bodies in DKA), lethargy, depression, and diarrhea may develop once concentrations reach 0.32 mmol/l. Oversupplementation of phosphorus should be avoided as hypocalcemia or metastatic calcification may result (9). Magnesium (total serum) is not usually measured routinely, but concentrations may be abnormal in DKA. A recent study in cats demonstrated high total serum magnesium concentrations at presentation in patients with DKA; however, after 48 hours of therapy, total serum magnesium concentrations were significantly decreased (10). Magnesium deficiency may be caused by poor oral intake, decreased intestinal absorption, increased renal loss, or changes in distribution as it is the second most abundant intracellular cation (11). Clinical signs of hypomagnesemia include neuromuscular weakness and cardiac arrhythmias, signs that can be seen with other electrolyte alterations. Hypomagnesemia can also cause decreases in other electrolytes such as potassium and calcium. Correction of deficits may resolve electrolyte disturbances and may improve clinical outcome in the severely deficient patient (Table 1). Liver enzyme elevations are common in diabetes mellitus. Further increases potentially occur in DKA. Alanine aminotransferase and aspartate aminotransferase are most commonly affected and these increase secondary to hypovolemia and poor hepatic blood flow, and subsequent hepatocellular damage (3). Further increases in serum alkaline phosphatase concentration may occur if pancreatitis and secondary cholestasis ensue. Cholesterol and triglycerides may be elevated secondary to derangements of lipid metabolism due to decreased insulin. Metabolic acidosis is one of the most prominent features of DKA. As ketone bodies accumulate in the blood and overwhelm the body s buffering capabilities, there is an increase in hydrogen ions and a decrease in bicarbonate. As dehydration worsens, blood flow to peripheral tissues decreases and the resulting lactic acidosis may contribute to the acid base derangement. Acidosis can be manifested as lethargy, vomiting, hyperventilation, decreased myocardial contractility, peripheral vasodilation, stupor, and coma. Initiation of insulin therapy to stop ketogenesis and fluid therapy to correct dehydration will help improve the metabolic acidosis in most patients. Bicarbonate supplementation should be pursued with caution and is generally not recommended unless the patient s blood ph is less than 7.1 or the serum bicarbonate is less than 12 mmol/l (Table 1). In DKA, ketones become unmeasured anions as they dissociate from ketoacids (12). If, however, significant dehydration is present secondary to the osmotic diuresis and vomiting, lactic acidosis secondary to tissue hypoxia may contribute to the unmeasured anions, thus increasing the anion gap. Anion gap may be normal or elevated. An elevated value further characterizes the metabolic acidosis caused by DKA. The anion gap is a representation of the circulating anions not routinely measured on biochemical analyses. The normal anion gap ranges from 10 to 20 and is calculated by the following equation: Osmolality (mosm) = 2(Na + K meq/l) + (glucose mmol/l) + (BUN mmol/l) Circulating urea and creatinine concentrations may be within reference range or high. These values are high in most patients as a reflection of severe dehydration, but renal insufficiency or failure is also a possible cause for the elevation. Elevations of urea and creatinine must be evaluated in light of the urine specific gravity. A low urine specific gravity at presentation does not always guarantee a diagnosis of renal insufficiency or failure, as Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 28 of 60

30 osmotic diuresis and chronic hypokalemia can contribute to low specific gravities in diabetic patients. Therefore, re-evaluation of urea, creatinine, and urine specific gravity must be done after treatment of the crisis. If urea and creatinine are initially elevated and remain static or increase with appropriate therapy, concurrent renal disease is strongly suspected. The most important part of urinalysis is measurement of glucose and ketones. A strongly positive glucose confirms diabetes mellitus and a positive result for ketones confirms DKA. A negative ketone result, however, does not definitively rule out ketosis. The nitroprusside reagent used in urine sticks detects only acetoacetate and acetone. It is not as sensitive for beta-hydroxybutyrate, the most prevalent ketone body, and therefore may be negative in the face of ketosis. A recent study reported that beta-hydroxybutyrate concentrations above 1.9 mmol/l were the most sensitive indicator of DKA and that values above 4.8 mmol/l were highly specific for its diagnosis (13). Using a cut-off value of 3.8 mmol/l was associated with the best combination of specificity (95%) and sensitivity (72%) for DKA. The presence of pyuria and hematuria on urinalysis, along with confirmation by examination of urine sediment, supports the presence of a urinary tract infection. Urine culture should be performed, however, regardless of urine sediment activity. The hemogram may be normal at presentation, but usually reveals a leukocytosis with a mature neutrophilia (common in cats), or a stress leukogram. There may be a regenerative or degenerative left shift suggestive of a severe inflammatory and/or infectious process. The red blood cell count and hematocrit may be elevated due to dehydration. Heinz bodies, with or without anemia, may be noted in cats, as feline hemoglobin is uniquely susceptible to oxidative damage (14). Treatment Treatment of diabetic ketoacidosis is outlined in Table 1 and includes the following steps in order of importance: 1) fluid therapy using 0.9% saline initially, followed by 2.5% or 5% dextrose as serum glucose falls; 2) insulin therapy (low-dose intramuscular or intravenous); 3) electrolyte supplementation (potassium, phosphorus, magnesium); and 4) reversal of metabolic acidosis. Fluid Therapy Fluid therapy should consist of 0.9% NaCl supplemented with potassium when insulin therapy is initiated; however, hypernatremic patients may be rehydrated with lactated Ringer s solution to limit sodium load. Placement of a large central venous catheter is preferred for intravenous access because central venous pressure (CVP) may be monitored thereby providing the means to avoid overhydration. In addition, the need for repeated venipuncture necessary for frequent monitoring of glucose, electrolytes, and blood gases is eliminated. Rapid initiation of fluid therapy is key for successful treatment of the DKA patient. Fluid rates vary depending on degree of dehydration, maintenance requirements, continuing losses such as vomiting and diarrhea, and presence of diseases such as congestive heart failure and renal disease. Extreme caution should be exercised when considering initiating fluid therapy with a hypotonic solution as this increases the risk of cerebral edema. Fluids containing dextrose may be required to maintain blood glucose concentrations as insulin treatment for the DKA is continued. Insulin Therapy In dogs, insulin therapy should be initiated using either intravenous insulin or low-dose intramuscular methods. Intravenous constant rate infusion (CRI) of regular insulin therapy is accomplished by placement of two catheters: a peripheral catheter for the insulin infusion, and a central catheter for sampling blood and administration of drugs and other fluids. A dosage of 2.2 U/kg for dogs or 1.1 U/kg for cats of regular (neutral, Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 29 of 60

31 soluble) insulin is diluted in 250 ml of saline. Approximately 50 ml of fluid and insulin are allowed to run through the intravenous drip set and is discarded because insulin binds to the plastic tubing. The species of regular insulin (beef, pork, or human) does not affect response; however, the type of insulin given is very important. Regular or synthetic short-acting insulin must be used; lente, glargine, isophane, or protamine zinc insulins should never be given intravenously. Using intravenous insulin administration, blood glucose decreases to below 15 mmol/l by approximately 10 and 16 hours in dogs and cats, respectively. Once this has been achieved, the animal is maintained on subcutaneous (SC) regular insulin ( U/kg SC every 4 6 hours) until it starts to eat and/or the ketosis has resolved. Often, the transition from hospital to home maintenance therapy can be made by using a low dose (1 2 U) of regular insulin combined with the intermediate or long-acting maintenance insulin at the recommended dosages. Electrolyte and Acid Base Therapy Potassium should be supplemented as soon as insulin therapy is initiated. While serum potassium may be normal or elevated in DKA, the animal actually suffers from total body depletion of potassium. Correction of the metabolic acidosis tends to drive potassium intracellularly in exchange for hydrogen ions. Insulin facilitates this exchange and the net effect is a dramatic decrease in serum potassium which must be attenuated with appropriate potassium supplementation in fluids. Refractory hypokalemia may be complicated by hypomagnesemia. Supplementation of magnesium along with potassium as outlined in Table 1 may be indicated in cats or dogs with hypokalemia that is unresponsive to potassium chloride supplementation. Serum and tissue phosphorus may also be depleted during a ketoacidotic crisis and some of the potassium supplementation should consist of potassium phosphate (one third of the potassium dose as potassium phosphate), particularly in small dogs and cats who are most susceptible to hemolysis caused by hypophosphatemia. Caution should be used as oversupplementation of phosphorus can result in metastatic calcification and hypocalcemia. Bicarbonate therapy may be necessary in some patients with blood ph less than 7.1 or if serum HCO 3 is less than 12 mmol/l. Caution is recommended as metabolic alkalosis may be difficult to reverse. Hyperosmolar nonketotic diabetic mellitus requires similar treatment to DKA but on a much slower time scale. Correct fluid and electrolyte imbalances very slowly. Fluid therapy is typically either 0.9% NaCl or 0.45% NaCl which replaces Na + for glucose in the extracellular fluid (ECF) spaces. Caution must be exercised to not decrease osmolality too quickly: decrease osmolality by ½ to 1 osmol/hour. The goal should be to correct dehydration over 36 hours. While patients may still be hypokalemic, this abnormality does not tend to be as severe as in DKA because they do not have as great of an osmotic diuresis. Patients with hyperosmolar diabetes may be hyperphosphatemic depending on the azotemia. Hypophosphatemia is less of a concern in hyperosmolar nonketotic diabetic mellitus. Insulin therapy is the same as for DKA but should be monitored very closely! Monitor urine output, electrolytes, and renal values one to three times daily. Monitoring Response to Treatment Fluid therapy is one of the cornerstones of treatment of the diabetic patient but overhydration is a concern, especially in cats or if renal or cardiac disease is present. With a central venous catheter in place, CVP can be monitored intermittently. Oscillometric or Doppler measurements can be used to monitor systemic blood pressure. Monitoring lead II electrocardiograms (ECGs) can also be helpful not only if cardiac disease is present, but in alerting the clinician that serious electrolyte abnormalities may be developing, warranting more frequent electrolyte analyses and alteration of electrolyte replacement therapy. Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 30 of 60

32 Hypokalemia may cause supraventricular and ventricular arrhythmias such as premature atrial and ventricular contractions, sinus bradycardia, paroxysmal atrial or junctional tachycardia, atrioventricular block, ventricular tachycardia, and ventricular fibrillation. Other ECG changes include ST segment depression, QT prolongation, and decreased amplitude and biphasic T waves (15). Electrocardiographic signs of hyperkalemia include decreased P wave amplitude, prolonged PR and QRS intervals, decreased R wave amplitude, ST segment depression and increased amplitude and sharply pointed T waves, bradycardia, atrial standstill, and ventricular fibrillation. Blood glucose should be checked every one to two hours during initial therapy, especially if administering insulin via CRI or hourly intramuscular (IM) injections because hypoglycemia is a common and avoidable complication of therapy. Use of glucometers, which require only a drop of blood, allows measurement of glucose without induction of anemia. Electrolyte values can change rapidly with initiation of therapy and thus should be monitored every 4 hours. For the first 24 to 48 hours of therapy, blood glucose concentrations should not decline below 12 mmol/l as lower values may predispose the patient to development of cerebral edema. After the first day or two, if the patient is responding to therapy, or if giving injections only every 4 to 6 hours, the frequency of blood glucose determinations can be reduced (ie, every 4 to 6 hours). More objective measurements of hydration status include direct or indirect blood pressure measurements, as well as measuring CVP, urine output and specific gravity, body weight, serum osmolality, PCV, and total solids. Assessing the PCV and plasma for evidence of hemolysis in the hypophosphatemic patient is important to evaluate for hemolytic anemia. Initially monitoring urine output via an indwelling urinary catheter connected to a closed system is also optimal to ensure the patient is not oliguric or anuric; this is especially important for the hyperosmolar patient as severe hyperglycemia (> 30 mmo/l) is unlikely to occur without significant renal impairment or severe dehydration and subsequent poor renal perfusion. A minimum of 1.0 to 2.0 ml urine per kilogram of body weight per hour should be produced. If output is less than optimal, check patency of the catheter, adequacy of fluid administration (CVP, arterial blood pressure, subjective signs, PCV/total solids, urine specific gravity), and adjust therapy as needed. Serum electrolytes and blood gas analyses should be performed four to six times daily during the first 24 to 48 hours when the patient is most critical. Electrolyte composition of the fluids may need to be altered several times daily depending on results of electrolyte analyses. Performing a urine dipstick test daily is also important to assess degree of glucosuria and ketonuria. An increase in dipstick ketones may actually be indicative of successful therapy as the dipstick measures acetoacetic acid, the metabolite of the most prevalent ketone body, beta-hydroxybutyric acid. Prognosis The prognosis for diabetic ketoacidosis in dogs is fair to good as long as the underlying disorder is treatable (eg, urinary tract infection, pneumonia). With acute pancreatitis, the prognosis depends on the severity of the pancreatic disease in both dogs and cats. Cats with hyperosmolar nonketotic or mixed ketotic syndrome have a very poor prognosis. References 1. Connaly HE. Critical care monitoring considerations for the diabetic patient. Clin Tech Small Anim Pract. 2002;17(2): Feldman EC, Nelson RW. Diabetic ketoacidosis, in Feldman EC, Nelson RW (eds): Canine and Feline Endocrinology and Reproduction, ed 2. Philadelphia: WB Saunders Co, 1996, pp Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 31 of 60

33 3. Crenshaw KL, Peterson ME. Pretreatment clinical and laboratory evaluation of cats with diabetes mellitus: 104 cases ( ). J Am Vet Med Assoc. 1996;209(5): Kerl ME. Diabetic ketoacidosis: Pathophysiology and clinical and laboratory presentation. Compend Contin Educ Pract Vet. 2001;23(3): Macintire DK. Emergency therapy of diabetic crises: Insulin overdose, diabetic ketoacidosis, and hyperosmolar coma. Vet Clin North Am: Small Anim Pract. 1995;25(3): Bruskiewicz KA, Nelson RW, Feldman ED, Griffey SM. Diabetic ketosis and ketoacidosis in cats: 42 cases ( ). J Am Vet Med Assoc. 1997;211(2): Greco DS. Endocrine emergencies. Part I. Endocrine pancreatic disorders. Compend Contin Educ Pract Vet. 1997;19(1): Wheeler SL. Emergency management of the diabetic patient. Sem Vet Med Surg (Small Anim). 1988;3(4): Nichols R, Crenshaw KL. Complications and concurrent disease associated with diabetic ketoacidosis and other severe forms of diabetes mellitus. Vet Clin North Am: Small Anim Pract. 1995;25(3): Norris CR, Nelson RW, Christopher MM. Serum total and ionized magnesium concentrations and urinary fractional excretion of magnesium in cats with diabetes mellitus and diabetic ketoacidosis. J Am Vet Med Assoc. 1999;215(10): Hansen B. Disorders of magnesium, in Dibartola SP (ed): Fluid Therapy in Small Animal Practice, ed 2. Philadelphia: WB Saunders Co, 2000, pp Bruyette DS. Diabetic ketoacidosis. Sem Vet Med Surg (Small Anim). 1997;12(4): Duarte R, Simoes DM, Franchini MI, et al. Accuracy of serum beta-hydroxybutyrate measurements for the diagnosis of diabetic ketoacidosis in 116 dogs. J Vet Intern Med. 2002;16(4): Christopher MM, Broussard JD, Peterson ME. Heinz body formation associated with ketoacidosis in diabetic cats. J Vet Intern Med. 1995;9(1): Smith FWK, Hadlock DJ. Electrocardiography, in Miller MS, Tilley LP (eds): Manual of Canine and Feline Cardiology, ed 2. Philadelphia: WB Saunders Co, 1995, pp Diehl KJ. Long-term complications of diabetes mellitus. Part II: Gastrointestinal and infectious. Vet Clin North Am: Small Anim Pract. 1995;25(3), Kerl ME. Diabetic ketoacidosis: Treatment recommendations. Compend Contin Educ Pract Vet. 2001;23(4): Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 32 of 60

34 Table 1: Stepwise Treatment of Diabetic Ketoacidosis (*) STEP ONE: FLUIDS a. Place intravenous catheter, preferably central venous b. Fluid rate: Estimate dehydration deficit (%) x BW (kg) x 1000 ml = no.of ml to rehydrate Estimate maintenance needs: 2.5 ml/kg/hr x no. of hours required to rehydrate (24 hours) Estimate losses (vomiting, diarrhea): Dehydration deficit + maintenance + losses = no. of ml of fluid/24 hours = hourly fluid rate c. Fluid composition Blood glucose Fluids > 15 mmol/l 0.9% NaCl % NaCl 8 12 plus 2.5 % 6 8 dextrose <6 same 0.45% NaCl plus 5% dextrose Rate up to 90 ml/kg/hr to rehydrate (see above) see above see above Route intravenous intravenous Monitor PCV, TS, Na, K, osmolality CVP, urine output Frequency q 4 hr q 2 hr STEP TWO: INSULIN Intravenous (Regular only), mixed in 250 ml NaCl 0.9%, discard 50 ml through IV tubing Blood glucose Rate Route Dose Monitor Frequency >15 mmol/l <6 10 ml/hr 7 ml/hr 5 ml/hr 5 ml/hr Stop IV, begin insulin q 4 hr IV IV IV IV SC 1.1 U/kg (C) or hyperosmola r 2.2 U/kg (D) U/kg Blood glucose q 1 2 hrs q 4 hrs q 2 hrs Intramuscular (Regular only) Blood glucose Rate > 15 mmol/l Initial dose q 1 hr < 15 q 4 6 hr q 6 8 hr Route IM IM IM SC Dose 0.2 U/kg 0.1 U/kg 0.1 U/kg U/kg Monitor Blood glucose Frequency Hourly Hourly q 4 6 hr q 6 8 hr STEP THREE: ELECTROLYTES Electrolyte concentration Potassium mmol/l <2.0 Amount (mmol/l) added to 1 L of fluids Maximum rate (ml/kg/hr) Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 33 of 60

35 Phosphorus mmol/l < mmol phosphate/kg/hr 0.03 mmol phosphate/kg/hr Monitor serum phosphorus q 6 hr Magnesium < 0.6 mmol/l STEP FOUR: ACID BASE BALANCE mmol/kg/day CRI MgCl, MgSO 4 Use 5% dextrose, Mg is incompatible with Ca and sodium bicarbonate solutions ph Bicarbonate concentration Dose of bicarbonate Rate < 7.1 < 12 mmol/l ml IV = 0.1 x BW (kg) x (24 HCO 3 ) over 2 hrs * Reprinted from Greco DS. Endocrine pancreatic emergencies. Compend Contin Educ Pract Vet. 1997;19(1):23-44; with permission). Abbreviations: C, cat; D, dog; BW, body weight; PCV, packed cell volume; TS, total solids; CRI, constant rate infusion; IV, intravenous; IM, intramuscular; SC, subcutaneous. Endocrinology Deborah S. Greco DVM, PhD, DACVIM Page 34 of 60

36 When It Looks Like Cushing s But Doesn t Test Like Cushing s Deborah S. Greco, DVM, PhD, Diplomate, ACVIM (Internal Medicine) Thomas Schermerhorn, VMD, Diplomate, ACVIM (Internal Medicine) The Patient Pumpkin, a 9-year-old, castrated, male miniature poodle had a 6- month history of endocrine alopecia. He had received multiple courses of antibiotics and one course of corticosteroids. No polydipsia or polyuria was observed. Pumpkin had evidence of external skin lesions as shown in Figure 1, and he was panting on presentation. Results of the clinical pathology workup are shown in Tables 1 and 2. Figure 1. Skin lesions observed on Pumpkin at the time of presentation. SPOT CHECK What initial screening tests do you want to run? Seminar veterinarians said: NAVC / WVC 1. UCCR 20% / 15% 2. ACTH stimulation test 31% / 36% 3. Low-dose dexamethasone suppression test 30% / 26% 4. Thyroid T 4, TSH, FT 4 D 14% / 16% 5. Bile acids 5% / 7% Answer: 1, 2, or 3 TABLE 1. CLINICAL PATHOLOGY RESULTS: PUMPKIN ALP 968 ALT 234 Cholesterol 425 NRBCs Stress leukogram Polycythemia Bile acids 25.9 Urine specific gravity Sediment Inactive Culture Negative Senior Care Endocrinology with Deborah Greco DVM, PhD, DACVIM Page 35 of 60

37 TABLE 2. ENDOCRINE TESTING: PUMPKIN When It Looks Like Cushing s But... T μg/dl TSH 0.2 ng/ml FT 4 D 24 nmol/l UCCR Positive, 85 Endogenous ACTH 75 pg/ml LDDS Baseline 3.4 μg/dl 3-hour 1.7 μg/dl 8-hour 1.2 μg/dl SPOT CHECK What is the correct interpretation of the endocrine tests? Seminar veterinarians said: NAVC / WVC 1. The tests are diagnostic for hyperadrenocorticism. 13% / 16% 2. The tests are diagnostic for hypothyroidism. 1% / 1% 3. The tests are inconclusive. 83% / 76% 4. The tests definitively rule out hyperadrenocorticism. 3% / 6% Answer: 3 Physical Examination At a follow-up visit 3 months later, the owners were concerned that Pumpkin was still panting and that the alopecia was still present. Physical examination disclosed a small (4 mm) mass adjacent to the anus, but the rectal examination was normal. The mass was aspirated (see Figure 2). Figure 2. Aspiration cytology. Pumpkin returned for a follow-up visit after 3 months at which time on physical examination a 4 mm mass was detected adjacent to the anus and an aspiration sample was collected. His rectal examination was otherwise normal. SPOT CHECK What is your next step? Seminar veterinarians said: NAVC / WVC 1. Abdominal ultrasound 45% / 41% 2. Repeat the LDDS test 16% / 22% 3. High-dose dexamethasone suppression test 11% / 5% 4. ACTH stimulation test with sex steroid analysis 28% / 30% 5. Treat 2% / 2% Answers: 1 and 4 Abdominal ultrasonography is a sensitive method of identifying adrenal tumors. Figure 3 shows results following ultrasonography of Pumpkin s abdomen. A sex steroid analysis was also done, and results are shown in Table 3. SPOT CHECK What is your interpretation of the cytology (see Figure 2)? Seminar veterinarians said: NAVC / WVC 1. Perianal adenoma 68% / 67% 2. Anal sac carcinoma 13% / 15% 3. Lymphoma 9% / 9% 4. Sebaceous adenoma 11% / 9% Answer: 1 Figure 3. Hyperechoic nodules are evident on each pole (arrows), and there is a 1.35 cm cyst in the cranial pole. Abdominal ultrasonography is a sensitive method of identifying adrenal tumors. 12 Senior Care 2003 Endocrinology with Deborah Greco DVM, PhD, DACVIM Page 36 of 60

38 TABLE 3. SEX STEROID ANALYSIS: PUMPKIN Pumpkin (ng/ml) Normal (ng/ml) Cortisol, baseline Cortisol, postprandial α-OH progesterone, postprandial Androstenedione, postprandial Progesterone, postprandial DHEAS, postprandial When It Looks Like Cushing s But... Case Management SPOT CHECK How should this dog be treated? Seminar veterinarians said: NAVC / WVC 1. Surgery 71% / 61% 2. Radiation 1% / 5% 3. Medical 28% / 34% Answer: 1 SPOT CHECK If you chose medical, which treatment would you use? NAVC seminar veterinarians said: 1. Mitotane 74% 2. Trilostane 2% 3. Ketoconazole 9% 4. Anipryl 15% Answer: 1 Pumpkin s adrenal tumor was surgically removed. He was prepared for surgery with a low dose (5 mg intramuscularly) of methylprednisolone acetate (Depo-Medrol Pfizer Animal Health). Following his recovery from the surgical procedure, Pumpkin was sent home on a regimen of 2.5 mg of prednisolone once daily for 2 weeks, then every other day for 2 weeks. Hyperadrenocorticism/Cushing s Syndrome Diagnosis of hyperadrenocorticism, or Cushing s syndrome, in dogs may be challenging. The following sections review the etiology 1-3, common signalment 1,2, clinical signs 1,4-12 and laboratory findings 1-16 associated with the disease and then explore medical, surgical, and radiation treatment options. Etiology Hyperadrenocorticism (HAC) may be divided into two broad categories. One category, pituitary-dependent hyperadrenocorticism, arises from adenomatous enlargement of the pituitary gland resulting in excessive adrenocorticotropin (ACTH) production. The other category, adrenaldependent disease, is associated with functional adenomas or adenocarcinomas of the adrenal gland. Ectopic ACTH secretion has not been reported in dogs; however, in humans ectopic ACTH secretion is associated with certain lung tumors. Iatrogenic HAC results from chronic excessive exogenous steroid administration. Figure 4 illustrates the various forms of HAC. Signalment Hyperadrenocorticism is found in middle-aged to older dogs (7 to 12 years of age); approximately 85% have pituitary-dependent hyperadrenocorticism (PDH), and 15% suffer from adrenal tumors. Breeds in which PDH is commonly seen include the miniature poodle, dachshund, boxer, Boston terrier, and beagle. Large-breed dogs often suffer from adrenal tumors, and there is a distinct female (3:1) predilection. History and Clinical Signs The most common clinical signs associated with canine HAC are polydipsia, polyuria, polyphagia, heat intolerance, lethargy, abdominal enlargement or pot belly, panting, obesity, muscle weakness, and recurrent urinary tract infections. 1,4-9 Dermatologic manifestations of canine HAC can Senior Care Endocrinology with Deborah Greco DVM, PhD, DACVIM Page 37 of 60

39 Hyperadrenocorticism Hypothalamus ACTH ACTH ACTH ACTH When It Looks Like Cushing s But... Cortisol Cortisol Cortisol Normal Cortical Adenoma or Carcinoma Corticotroph Adenoma Adenohypophysis Idiopathic Cortical Hyperplasia ACTH ACTH Cortisol Cortisol ACTH Iatrogenic Ectopic ACTH Secretion Figure 4. Various etiologies of canine and feline hyperadrenocorticism. include alopecia (especially truncal), thin skin, phlebectasias, comedones, bruising, cutaneous hyperpigmentation, calcinosis cutis, pyoderma, dermal atrophy (especially around scars), secondary demodicosis, and seborrhea. 9 Uncommon clinical manifestations of HAC in the dog can include such signs as hypertension, pulmonary thromboembolism, bronchial calcification or congestive heart failure and neurologic signs, such as polyneuropathy/myopathy, behavior changes, blindness, or pseudomyotonia. Evidence of hypercortisolemia may be evident as weakening of collagen manifesting as cranial cruciate rupture (small dog) or corneal ulceration (nonhealing). Finally, reproductive signs of HAC can include perianal adenoma in a female or castrated male, clitoral hypertrophy in females, testicular atrophy in intact males, or prostatomegaly in male castrated dogs. 4,5,10-12 Laboratory Abnormalities CLINICAL CLIPBOARD The most common clinical signs associated with canine HAC are polydipsia, polyuria, polyphagia, heat intolerance, lethargy, abdominal enlargement or pot belly, panting, obesity, muscle weakness, and recurrent urinary tract infections. In dogs, serum chemistry abnormalities associated with hypercortisolemia include increased serum alkaline phosphatase (ALP), increased alanine transferase (ALT), hypercholesterolemia, hyperglycemia, and decreased BUN. 14,15 The hemogram is characterized by evidence of regeneration (erythrocytosis, nucleated red blood cells [NRBCs]) and a classic stress leukogram (eosinopenia, lymphopenia, and mature 14 Senior Care 2003 Endocrinology with Deborah Greco DVM, PhD, DACVIM Page 38 of 60

40 leukocytosis). Basophilia is occasionally observed. 1,5,9 Many dogs with HAC have subclinical urinary tract infection without pyuria (bacteriuria and positive culture) but lack pyuria or proteinuria, which is likely to be caused by glomerulosclerosis. 1,5,13,16 Thyroid status is often affected in animals with HAC, as evidenced by decreased basal thyroxine (T 4 ) and triiodothyronine (T 3 ), usually caused by euthyroid sick syndrome, and decreased endogenous thyroid-stimulating hormone (TSH) secretion, which can result from overcrowding of pituitary thyrotrophs. 17 Although less common in dogs than in cats, overt diabetes mellitus may result from the insulin antagonism caused by hypercortisolemia in about 25% of dogs with HAC. 15 Rarely, HAC can be a cause of insulin resistance and poor glycemic control in diabetics. Diagnostic Approach The diagnosis of HAC should be based on appropriate clinical signs (first and foremost) followed by supporting minimum database abnormalities (high cholesterol, SAP, etc) and confirmed via an appropriate screening test for HAC. 1,18,19 If screening test results are inconclusive (borderline, etc), or if laboratory abnormalities associated with HAC (increased SAP, etc) are noted in a dog without clinical signs of HAC, the dog should be retested at a later date (3 to 6 months) rather than be subjected to treatment for HAC without a definitive diagnosis. In particular, the diagnosis of sex steroid induced Cushing s disease may be especially difficult. SCREENING TESTS: DOES THE DOG SUFFER CLINICAL CLIPBOARD The diagnosis of HAC should be based on appropriate clinical signs (first and foremost) followed by supporting minimum database abnormalities (high cholesterol, SAP, etc) and confirmed via an appropriate screening test for HAC. FROM HYPERADRENOCORTICISM? Serum alkaline phosphatase (SAP) isoenzyme is a screening test available to the practitioner. The advantages of SAP isoenzyme measurement are wide availability and low CLINICAL CLIPBOARD If screening test results are inconclusive or if laboratory abnormalities associated with HAC are noted in a dog without clinical signs of HAC, the dog should be retested at a later date (3 to 6 months) rather than be subjected to treatment for HAC without a definitive diagnosis. cost ; however, even small elevations in serum cortisol, such as those that occur with exogenous steroid administration in ocular preparations, can induce SAP isoenzyme. This test has a very low specificity (<44%) because it is affected by stress and by nonadrenal disease. 22 Another disadvantage is that this test cannot differentiate between endogenous and iatrogenic HAC. The urine cortisol to creatinine ratio (UCCR) is highly sensitive in separating normal dogs from those with HAC, but the test is not highly specific for HAC because dogs with moderate to severe nonadrenal illness also exhibit elevated ratios Therefore, the UCCR test should be performed on a free-catch urine sample collected at home by the client. Even the stress associated with transportation to the veterinarian s office or restraint for cystocentesis, or both, can be enough to elevate a dog s cortisol level and cause a falsely elevated UCCR. Any abnormal UCCR should be confirmed with an ACTH stimulation test, an intravenous low-dose dexamethasone suppression (LDDS) test, or an oral LDDS test The LDDS test is considered the screening test of choice for canine HAC when it is properly used. 1,24,29 It is an extremely sensitive test (92% to 95%); only 5% to 8% of dogs with PDH exhibit suppressed cortisol concentrations at 8 hours (ie, 5% to 10% false negatives). 19,30 In addition, 30% of dogs with PDH exhibit suppression at 3 or 4 hours followed by escape of suppression at 8 hours; this pattern is diagnostic for PDH making further testing unnecessary. 19 The major disadvantage of the LDDS test is the lack of specificity in dogs with nonadrenal illness. Kaplan and Peterson recently reported that more than 50% of dogs with nonadrenal illness will have a positive LDDS test. 31 It is recommended that a dog be allowed to recover from the nonadrenal illness prior to testing for HAC with an LDDS test. 19 The adrenocorticotropin (ACTH) stimulation test When It Looks Like Cushing s But... Senior Care Endocrinology with Deborah Greco DVM, PhD, DACVIM Page 39 of 60

41 When It Looks Like Cushing s But... CLINICAL CLIPBOARD The LDDS test is considered the screening test of choice for canine HAC. The major disadvantage of the LDDS test is the lack of specificity in dogs with nonadrenal illness. It is recommended that a dog be allowed to recover from the nonadrenal illness prior to testing for HAC with an LDDS test. is used to diagnose a variety of adrenopathic disorders, including endogenous or iatrogenic HAC and spontaneous HAC. 8,29,32-34 As a screening test for the diagnosis of naturally occurring HAC, the ACTH response test has a diagnostic sensitivity of approximately 80% to 85% and a higher specificity than the LDDS test. 29,34 In the study by Kaplan and Peterson, only 15% of dogs with nonadrenal disease exhibited an exaggerated response to ACTH stimulation. 31 Adrenal tumors may be particularly difficult to diagnose using an ACTH stimulation test. 1,19 WHEN THE SIGNS INDICATE CUSHING S BUT THE TESTS DON T: DOCUMENTING ADRENAL SEX STEROID EXCESS Dogs suffering from adrenal sex steroid excess may have normal ACTH stimulation and LDDS tests because serum cortisol concentrations are normal. This may be due to excess cortisol precursors (Figure 5). Increases in progesterone, 17α-OH-progesterone, androstenedione, testosterone, and estrogens may require dynamic adrenal testing using the ACTH stimulation test and measurement of sex steroids in addition to cortisol. 35 Synthesis of Adrenal Steroids Mode of Action Cholesterol 3 β-hydrosysteroid- dehydrogenase Pregnenolone Progesterone 17 α-oh Pregnenolone 11-Deoxycorticosterone 17 α-oh Progesterone Dehydroepiandrosterone Aldosterone 11-Deoxycortisol CORTICOSTERONE CORTISOL Androstenedion Figure 5. Steroid synthesis pathway. 16 Senior Care 2003 Endocrinology with Deborah Greco DVM, PhD, DACVIM Page 40 of 60

42 DIFFERENTIATION TESTS: DOES THE DOG HAVE PITUITARY-DEPENDENT HYPERADRENOCORTICISM OR AN ADRENAL TUMOR? After the diagnosis of HAC has been confirmed, differentiation of pituitary-dependent versus adrenal-dependent disease may be necessary. Although the majority of dogs with HAC suffer from PDH, certain cases that are atypical (eg, the anorectic dog with HAC) should alert the clinician to the fact that a differentiation test is appropriate. In particular, differentiation of PDH (often macroadenomas) from adrenal tumor is often necessary in large-breed dogs. The high-dose dexamethasone suppression (HDDS) test works on the principle that autonomous ACTH hypersecretion by the pituitary can be suppressed by supraphysiologic concentrations of steroid. Dogs with autonomous cortisol-producing adrenal tumors have maximally suppressed ACTH production via the normal feedback mechanism; therefore, administration of dexamethasone, no matter how high the dose, cannot suppress serum cortisol concentrations in these dogs. 1,4 In dogs with PDH, however, the high dose of dexamethasone is able to suppress ACTH and, hence, cortisol secretion. One important caveat is that dogs with pituitary macroadenomas (15% to 50% of dogs with PDH) fail to suppress on the HDDS test. 1 Measurement of endogenous plasma ACTH concentrations is the most reliable method of discriminating between PDH and adrenal tumor. 36 Dogs with adrenal tumors have low to undetectable ACTH concentrations; in contrast, dogs with PDH exhibit normal to elevated ACTH concentrations. 36 Recently, researchers have found that the addition of the protease inhibitor, aprotinin, to whole blood in EDTA tubes inhibits the degradation of ACTH. 37 Samples may be collected, spun in a nonrefrigerated centrifuge, and kept for up to 4 days at <4º C. 37 Diagnostic imaging of the pituitary and the adrenal glands can be accomplished via abdominal radiography, ultrasonography, computed tomography, or magnetic resonance imaging. 38,39 Abdominal radiographs should be performed in all dogs that fail to suppress on an HDDS; approximately 30% to 50% of dogs with adrenal tumors exhibit a mineralized mass in the area of the adrenal glands. 38 A more sensitive method of identifying adrenal tumors is via abdominal ultrasonography. 38 In addition, liver metastasis or invasion into the vena cava may be demonstrated in dogs with adrenal carcinomas. Either computed tomography or magnetic resonance imaging, or both, of the brain or abdominal cavity in dogs that fail to suppress on the HDDS may demonstrate unilateral adrenal enlargement (50%), pituitary macroadenoma (25%), or pituitary microadenoma (25%) There is no single test or combination of tests that performs with 100% accuracy for making a diagnosis of HAC. The sensitivity and specificity of individual tests or combinations of tests to make an accurate diagnosis of HAC are increased when they are applied to a patient population that is likely to have HAC. Most of the tests used in the diagnosis of HAC are markedly affected by the presence of other, perhaps unrelated, disorders; and, as a result, these tests perform poorly when applied to dogs with nonadrenal illness. Proper patient selection is essential in order to get useful diagnostic information from such tests as the LDDS and UCCR, both of which have a high false-positive rate when applied to the general population of sick patients. Similarly, the results of the HDDS test are more meaningful when considered in light of results of imaging studies, a finding that underscores the need for an integrated diagnostic strategy in most patients. CLINICAL CLIPBOARD When It Looks Like Cushing s But... CLINICAL CLIPBOARD Dogs with adrenal tumors have low to undetectable ACTH concentrations; in contrast, dogs with PDH exhibit normal to elevated ACTH concentrations. There is no single test or combination of tests that performs with 100% accuracy for making a diagnosis of HAC. The sensitivity and specificity of individual tests or combinations of tests to make an accurate diagnosis of HAC are increased when they are applied to a patient population that is likely to have HAC. Senior Care Endocrinology with Deborah Greco DVM, PhD, DACVIM Page 41 of 60