hypercalcemia of malignancy hyperparathyroidism PHPT the most common cause of hypercalcemia in the outpatient setting the second most common cause

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1 hyperparathyroidism A 68-year-old woman with documented osteoporosis has blood tests showing elevated serum calcium and parathyroid hormone (PTH) levels: 11.2 mg/dl ( mg/dl) and 88 pg/ml (10-60), respectively. What is the diagnosis and the anatomic basis for this disease hyperparathyroidism is classified as primary, secondary, or tertiary, depending on the cause of excess PTH synthesis PHPT the most common cause of hypercalcemia in the outpatient setting hypercalcemia of malignancy hypercalcemia of malignancy the second most common cause of hypercalcemia 1

2 the most common cause of hypercalcemia in the inpatient setting hypercalcemia can occur in 30% of patients with cancer the most common cancers associated with hypercalcemia breast lung multiple myeloma three mechanisms of hypercalcemia of malignancy (1)release of cytokines by osteolytic metastases (2) tumor secretion of PTHrP (3) tumor production of calcitriol 2

3 osteolytic metastases tumor cells cytokines activate osteoclasts bony destruction osteolytic metastases osteolytic metastases account for 20% of cases of hypercalcemia of malignancy, and breast cancer is the most frequent primary tumor solid tumors secretion of PTHrP this condition is termed humoral hypercalcemia of malignancy the most common cause of hypercalcemia in patients with nonmetastatic solid tumors is secretion of PTHrP by the tumor secretion of PTHrP by the tumor accounts for the remaining 80% of cases of hypercalcemia caused by malignancy 3

4 primary hyperparathyroidism intrinsic abnormality of one or more of the parathyroid glands the abnormal parathyroid gland secretes PTH inappropriately relative to the serum ionized calcium level under normal conditions, the serum calcium level is tightly regulated within a narrow range as a result of the exquisite responsiveness of parathyroid cells to circulating calcium Broken Physiology patients with PHPT develop a new set-point in one or more parathyroid glands, such that a higher circulating level of calcium is maintained circulating PTH increase osteoclast activity excess calcium is released into the blood 4

5 increased renal absorption of calcium and increased absorption of calcium from the GI tract pathology parathyroid adenoma multigland disease 85% of patients with PHPT have single parathyroid gland enlargement parathyroid adenoma familial syndromes are associated with multigland PHPT familial syndromes MEN1 MEN2A Patients with MEN1 invariably have enlargement of all parathyroid glands, whereas patients with MEN2A generally have asymmetrical parathyroid gland enlargement and normal-appearing parathyroid glands 5

6 parathyroid carcinoma 0.7% to 2.1% of cases of PHPT an array of symptoms nephrolithiasis osteopenia and osteoporosis decreased cognitive function lethargy GI disturbances musculoskeletal abnormalities often difficult to prove that these nonspecific findings result from PHPT because they are common in the general population secondary hyperparathyroidism physiologic secretion of PTH by the parathyroid glands in response to hypocalcemia 6

7 vitamin D deficiency chronic renal failure (uremic hyperparathyroidism) regardless of the cause of secondary hyperparathyroidism, hyperplasia of all parathyroid glands develops in contrast to patients with PHPT, less than 1% of patients with uremic secondary HPT require surgical intervention tertiary hyperparathyroidism represents an advanced form of secondary HPT; it is seen in patients with longstanding chronic renal failure and in patients who have persistent autonomous secretion of PTH after renal transplantation loss of response to serum calcium levels leads to fourgland hyperplasia with autonomous activity 7

8 this form of HPT can be lifethreatening, and all patients with tertiary HPT should be referred for surgical intervention hypercalcemic crisis medical and surgical emergency Definition significantly elevated serum calcium level in association with end-organ dysfunction no specific level of hypercalcemia, it generally occurs when serum calcium exceeds 14 mg/dl life-threatening hypercalcemia often occurs in patients with underlying malignancy 8

9 One treatment should be initiated immediately patients are severely dehydrated effective therapy begins with aggressive fluid resuscitation with normal saline, at a rate of at least 200 ml/hr to promote renal excretion of calcium as well as to restore intravascular volume Two once the patient is rehydrated, a diuretic may be added to inhibit calcium resorption Three dialysis is used in patients with renal failure who cannot tolerate large-volume resuscitation medications Glucocorticoids Calcitonin Bisphosphonates 9

10 Calciphylaxis calcific uremic arteriolopathy a syndrome of vascular calcification, thrombosis, and skin necrosis seen in patients with (ESRD) and results in chronic nonhealing wounds and can be fatal The diagnosis of calciphylaxis is a clinical one extensive Ischemic areas of violaceous skin necrosis associated with severe pain 10

11 necrotic skin may become infected, leading to sepsis skin biopsy bone scintigraphy skin biopsy small arterial calcification and occlusion in the absence of vasculitis bone scintigraphy increased tracer accumulation in the soft tissues prevention is crucial Rigorous and continuous control of phosphate and calcium balance may avoid the metabolic changes associated with calciphylaxis 11

12 urgent parathyroidectomy urgent operation and aggressive subtotal parathyroidectomy is recommended once the diagnosis is established diagnosis of PHPT The diagnosis of PHPT is biochemical the serum PTH is "inappropriate" elevated intact PTH levels in the setting of elevated serum calcium confirms the diagnosis in patients with normal renal function 12

13 a subset of patients with PHPT have hypercalcemia in the setting of a normal intact PTH level the serum PTH is "inappropriate" because it should be suppressed by hypercalcemia Who should have parathyroidectomy surgery is the only curative treatment for PHPT with excellent operative success and complication profile All symptomatic patients should be considered surgical candidates asymptomatic patients most recent guidelines published in

14 parathyroidectomy for asymptomatic patients younger than 50 years of age, with serum calcium levels over 1 mg/dl above the upper limit of normal, creatinine clearance less than 60 ml/min, bone mineral density T score of 2.5 or lower at any site, or previous bone fracture fragility Does asymptomatic primary hyperparathyroidism really exist? Although most cases of PHPT are classified as asymptomatic, defining "truly asymptomatic" PHPT can be difficult. many symptoms associated with PHPT (e.g., fatigue, bone pain, and GI symptoms) are nonspecific and not attributed to PHPT Most patients do not realize the severity of their symptoms until they undergo parathyroidectomy and experience symptomatic relief. diagnosis of PHPT is made patients meet surgical criteria imaging studies localize abnormal glands 14

15 Parathyroid Gland Localization The purpose The purpose of imaging is to assist the surgeon in planning and performing an appropriate operation Localization studies aid parathyroid surgery; they should not be used for diagnosis because the diagnostic criteria for PHPT are based on biochemical data Localization decreased extent of surgical dissection/operative time, and concurrent thyroid disease may be identified, allowing for combined surgical procedures Technetium 99m ( 99m Tc) sestamibi scintigraphy 15

16 A technique to differentiate sestamibi uptake by abnormal parathyroid and thyroid tissue. This involves a dual radionuclide approach combined imaging modalities sestamibi with (CT) sestamibi and cervical ultrasound Parathyroidectomy It is important that the surgeon and the patient understand that any planned procedure may be altered in the operating room, depending on the findings What is removed Single gland adenoma, a total parathyroidectomy with immediate heterotopic transplantation of parathyroid tissue or a subtotal parathyroidectomy is required 16

17 Surgical Options Bilateral Neck Exploration unilateral minimally invasive approach Bilateral neck exploration (BNE) has long been the gold standard operation for PHPT. It involves direct visualization of all parathyroid glands, with removal of enlarged parathyroid tissue Patients with a single parathyroid adenoma undergo curative resection after the parathyroid adenoma is removed If the patient has multigland hyperplasia, either a total cervical parathyroidectomy with immediate heterotopic transplantation of parathyroid tissue to a convenient location (usually the forearm) or a subtotal parathyroidectomy is required unilateral minimally invasive parathyroidectomy Rationale 85% of patients with PHPT have single-gland disease 17

18 key to a successful outcome preoperative localization rapid intraoperative PTH assay 18