Endocrine System Physiology

Transcription

1 M53_MARI0000_00_SE_EX04.qxd 7/15/11 4:32 PM Page E X E R C I S E Endocrine System Physiology Advance Preparation/Comments Consider covering the following topics to prepare students for the simulation: Describe the regulation of thyroid hormone secretion. Explain the relationship between the hypophysis (pituitary gland) and the hypothalamus. Describe the synthesis of thyroid hormones, thyroxine and triiodothyronine. Explain disorders that result in goiter formation. Review the factors that contribute to bone density. Explain the regulation of blood glucose levels and the types of diabetes mellitus. Describe the regulation of glucocorticoid release from the adrenal gland. Describe the diseases associated with glucocorticoid imbalance. Answers to Questions/Experimental Data Pre-lab Quiz in the Lab Manual 1. Metabolism is defined as all of the chemical reactions that are necessary to maintain life. 2. Catabolism 3. Thyroid hormone 4. Control 5. b. increased in individuals with hyperthyroidism 6. c. oxygen 7. True 8. insulin Activity 1: Metabolism and Thyroid Hormone (pp. PEx-60 PEx-64) 1h ml 1i Predict Question 1: The BMR of both remaining rats will be lower than the normal rat s BMR Predict Question 2: The normal rat will become hyperthyroidic but will not develop a goiter. Predict Question 3: The normal rat will become hyperthyroidic and develop a goiter. Predict Question 4: The normal rat will become hypothyroidic and develop a goiter. 369

2 M53_MARI0000_00_SE_EX04.qxd 7/15/11 4:32 PM Page 370 Chart 1: Effects of Hormones on Metabolic Rate Normal rat Thyroidectomized rat Hypophysectomized rat Baseline Weight (g) Variable, Variable, Variable, used in 1 minute Variable, Variable, Variable, used per hour * * * Metabolic rate /kg/hr* /kg/hr* /kg/hr* Palpation results No mass No mass No mass With thyroxine Weight (g) Same as baseline Same as baseline Same as baseline used in 1 minute Variable, Variable, Variable, used per hour ml ml ml Metabolic rate /kg/hr /kg/hr /kg/hr Palpation results No mass No mass No mass With TSH Weight (g) Same as baseline Same as baseline Same as baseline used in 1 minute Variable, Variable, Variable, used per hour ml /kg/hr ml ml Metabolic rate 1904 /kg/hr /kg/hr /kg/hr Palpation results 1904 /kg/hr Mass No mass Mass With propylthiouracil Weight (g) Same as baseline Same as baseline Same as baseline used in 1 minute Variable, Variable, Variable, used per hour ml ml ml Metabolic rate /kg/hr /kg/hr /kg/hr Palpation results Mass No mass No mass * Data populated by student calculations. 1. The carbon dioxide is absorbed by the soda lime in the bottom of the glass chamber. 2. The fluid levels would increase due to the additional oxygen utilized for the exercising rat. 3. The hypothalamus secretes TRH which stimulates the release of TSH by the pituitary gland. TSH stimulates the thyroid gland to produce thyroxine. 4. A tropic hormone stimulates or inhibits another endocrine gland to secrete hormones. 5. Thyroidectomized rats could be treated with thyroxine to replace the hormone that is not available because the thyroid gland is missing. 6. The hypothalamus secretes TRH which stimulates the release of TSH. 7. TRH travels from the hypothalamus to the pituitary gland via the hypothalamic-pituitary portal system. 8. TSH has no effect on the thyroidectomized rat because the rat doesn t have a thyroid gland to stimulate. 9. The administration of PTU had no effect on the thyroidectomized and hypophysectomized rats because they lack the glands required for the production of thyroxine. 10. The buildup of the precursors to thyroxine can occur if there is no available iodine to complete the thyroxine formation. The lack of iodine can also result in goiter. 370 Exercise 4

3 M53_MARI0000_00_SE_EX04.qxd 7/15/11 4:32 PM Page 371 Activity 2: Plasma Glucose, Insulin, and Diabetes Mellitus (pp. PEx-64 PEx-67) Predict Question 1: The optical density of the sample will be measured and the glucose concentration will be extrapolated from the glucose standard curve. Chart 2.1 Glucose Standard Curve Results Tube Optical density Glucose (mg/dl) Chart 2.2 Fasting Plasma Glucose Results Sample Optical density Glucose (mg/dl) The optical density should be proportional to the concentration of glucose producing a roughly straight line. An aberrant glucose standard curve would not produce a straight line. 2. Some potential sources of variability include experimental error in measurement of the reagents and inherent variability of the spectrophotometer measurements. 3. Patients in the borderline range should be counseled to alter their diet and exercise. Their diet should limit the ingestion of simple sugars and their exercise level should be increased. 4. Our current diet trends are contributing to an increase in the prevalence of Type II diabetes in children. Activity 3: Hormone Replacement Therapy (pp. PEx-67 PEx-69) Predict Question 1: The saline injections will not change the rat s vertebral bone density (indicated by an unchanging T score). Predict Question 2: The estrogen injections will increase the rat s vertebral bone density (indicated by a less-negative T score). Predict Question 3: The calcitonin injections will not change the rat s vertebral bone density (indicated by an unchanging T score). Chart 2.3 Hormone Replacement Therapy Results Rat T score Control Variable, 2.81 to 2.85 Estrogen Variable, 1.52 to 1.74 Calcitonin Variable, 2.05 to 2.35 Exercise 4 371

4 M53_MARI0000_00_SE_EX04.qxd 7/15/11 4:32 PM Page Student s answers will vary depending upon their research. Possibly they will describe estrogen therapy and the risks associated with this therapy. 2. The dosage of hormone replacement will be determined by the current levels of hormones found in the body using blood tests. Activity 4: Measuring Cortisol and Adrenocorticotropic Hormone (pp. PEx-69 PEx-70) Chart 4: Measurement of Cortisol Patient Cortisol (mcg/dl) Cortisol level ACTH (pg/ml) ACTH level 1 Variable, 3 1 Low* Variable, 18 2 Low* 2 Variable, 35 5 High* Variable, 13 2 Low* 3 Variable, 45 5 High* Variable, 86 5 High* 4 Variable, 3 1 Low* Variable, High* 5 Variable, 50 5 High* Variable, 18 2 Low* * The entries in these columns are designated by the student in the software. 1. The benefits of glucocorticoid therapy include dilation of the airway. The drawbacks are the side effects associated with long term treatment. These include high blood pressure, bone thinning, high blood sugar levels, suppression of the immune response and weight gain. 2. Cushing s syndrome is primary hypercortisolism resulting from an adrenal gland tumor. Cushing s disease is secondary hypercortisolism resulting from a pituitary tumor. 372 Exercise 4

5 M53_MARI0000_00_SE_EX04.qxd 7/15/11 4:32 PM Page 373 NAME LAB TIME/DATE R E V I E W S H E E T EXERCISE 4 Endocrine System Physiology A C T I V I T Y 1 Metabolism and Thyroid Hormone Part 1 1. Which rat had the fastest basal metabolic rate (BMR)? The normal rat had the fastest basal metabolic rate because it was not missing its pituitary gland or its thyroid gland. 2. Why did the metabolic rates differ between the normal rat and the surgically altered rats? How well did the results compare with your prediction? The normal rat has the highest BMR because it has the glands required to stimulate and regulate the release of thyroid hormones. 3. If an animal has been thyroidectomized, what hormone(s) would be missing in its blood? For the thyroidectomized rats the hormones missing will be triiodothyronine and thyroxine. 4. If an animal has been hypophysectomized, what effect would you expect to see in the hormone levels in its body? For the hypophysectomized rat, the TSH will be missing due to the missing pituitary gland. Part 2 5. What was the effect of thyroxine injections on the normal rat s BMR? The levels were a little off. The normal rat was hyperthyroidic because the thyroxine increases the metabolic rate but it did not develop goiter. 6. What was the effect of thyroxine injections on the thyroidectomized rat s BMR? How does the BMR in this case compare with the normal rat s BMR? Was the dose of thyroxine in the syringe too large, too small, or just right? The BMR increased for the thyroidectomized rat with thyroxine injections. The BMR was still a little bit below the normal rat s BMR with thyroxine. The dose was too low. 7. What was the effect of thyroxine injections on the hypophysectomized rat s BMR? How does the BMR in this case compare The BMR increased with the normal rat s BMR? Was the dose of thyroxine in the syringe too large, too small, or just right? for the hypophysectomized rat with thyroxine injections. The BMR was still a little bit below the normal rat s BMR with thyroxine. The dose was too low. 373

6 M53_MARI0000_00_SE_EX04.qxd 7/15/11 4:32 PM Page 374 Part 3 8. What was the effect of thyroid-stimulating hormone (TSH) injections on the normal rat s BMR? The effect of TSH was to increase the normal rat s BMR. 9. What was the effect of TSH injections on the thyroidectomized rat s BMR? How does the BMR in this case compare with the normal rat s BMR? Why was this effect observed? There was no effect on the thyroidectomized rat s BMR with the injection of TSH because there was no thyroid gland to stimulate. 10. What was the effect of TSH injections on the hypophysectomized rat s BMR? How does the BMR in this case compare with the normal rat s BMR? Was the dose of TSH in the syringe too large, too small, or just right? The hypophysectomized rat BMR increased with TSH. The BMR was just below the normal rat but still lower. the syringe amount was a little too low. Part What was the effect of propylthiouracil (PTU) injections on the normal rat s BMR? Why did this rat develop a palpable goiter? The effect of PTU injections on the normal rat was to decrease the BMR. The palpable goiter was due to the buildup of the precursors to thyroxine. 12. What was the effect of PTU injections on the thyroidectomized rat s BMR? How does the BMR in this case compare with the normal rat s BMR? Why was this effect observed? The effect of PTU injections on the thyroidectomized rat was not visible because there was no thyroid gland to be affected. 13. What was the effect of PTU injections on the hypophysectomized rat s BMR? How does the BMR in this case compare with the normal rat s BMR? Why was this effect observed? The effect of PTU injections on the hypophysectomized rat was not visible because the rat is missing the pituitary gland. ACTIVITY 2 Plasma Glucose, Insulin, and Diabetes Mellitus 1. What is a glucose standard curve, and why did you need to obtain one for this experiment? Did you correctly predict how you would measure the amount of plasma glucose in a patient sample using the glucose standard curve? The glucose standard curve correlates the intensity of the color obtained and measured on a spectrophotometer (optical density) to the glucose concentration. 2. Which patient(s) had glucose reading(s) in the diabetic range? Can you say with certainty whether each of these patients has type 1 or type 2 diabetes? Why or why not? Patients 3 and 5 had a fasting plasma glucose in the diabetic range. It is not possible to tell if they have type 1 or type 2 just from their fasting plasma glucose. 3. Describe the diagnosis for patient 3, who was also pregnant at the time of this assay. This would be described as gestational diabetes. The diabetes often disappears after the pregnancy. 374 Review Sheet 4

7 M53_MARI0000_00_SE_EX04.qxd 7/15/11 4:32 PM Page Which patient(s) had normal glucose reading(s)? Patients 1 and 2 were in the normal range. 5. What are some lifestyle choices these patients with normal plasma glucose readings might recommend to the borderline impaired patients? Limit the ingestion of simple sugars. Choose good carbohydrates such as whole wheat and fiber based carbohydrate choices. ACTIVITY 3 Hormone Replacement Therapy 1. Why were ovariectomized rats used in this experiment? How does the fact that the rats are ovariectomized explain their baseline T scores? The ovaries produce estrogen and estrogen stimulates bone growth. Without estrogen bone growth is impaired and osteoporosis is a common result. 2. What effect did the administration of saline injections have on the control rat? How well did the results compare with your prediction? The saline had no effect. The inclusion of the saline as a negative control is to insure that saline has no effect. 3. What effect did the administration of estrogen injections have on the estrogen-treated rat? How well did the results compare with your prediction? The estrogen injections did increase the rat s vertebral bone density as predicted and as indicated by the negative T score. 4. What effect did the administration of calcitonin injections have on the calcitonin-treated rat? How well did the results compare with your prediction? The calcitonin showed no change in the vertebral bone density. This is somewhat contradictory to what is expected. We do not know why. 5. What are some health risks that postmenopausal women must consider when contemplating estrogen hormone replacement therapy? Health risks of estrogen therapy include an increased incidence of uterine cancer, breast cancer and blood clots. ACTIVITY 4 Measuring Cortisol and Adrenocorticotropic Hormone 1. Which patient would most likely be diagnosed with Cushing s disease? Why? Patient 3 would be diagnosed with Cushing s disease because the levels of cortisol and ACTH are both high. 2. Which two patients have hormone levels characteristic of Cushing s syndrome? Patients 2 and 5 both have high levels of cortisol and low ACTH. These levels are characteristic of Cushing s syndrome. 3. Patient 2 is being treated for rheumatoid arthritis with prednisone. How does this information change the diagnosis? The diagnosis would change to iatrogenic or physician-induced Cushing s syndrome. 4. Which patient would most likely be diagnosed with Addison s disease? Why? Patient 4 would be diagnosed with Addison s disease because the level of ACTH is high but the level of cortisol is low. Review Sheet 4 375