endocrine and metabolic disorders
Hypercalcemia
Pathophysiology of Hypercalcemia
 Primary hyperparathyroidism is a generalized disorder resulting from excessive secretion of PTH increases serum calcium by increasing intestinal absorption of calcium; rapidly mobilizing calcium and phosphate from bone (bone resorption); enhancing renal distal nephron calcium reabsorption; and stimulating conversion of Vitamin D Deficiency and Dependency to its most active form, Familial forms due to Parathyroid adenoma occur in patients with other endocrine tumors (see also Although asymptomatic hypercalcemia is the most frequent presentation, Urinary Calculi is also common, particularly when hypercalciuria occurs due to long-standing hypercalcemia. Histologic examination shows a parathyroid adenoma in about 85% of patients with primary hyperparathyroidism, although it is sometimes difficult to distinguish an adenoma from a normal gland. About 15% of cases are due to hyperplasia of≥2 glands. Parathyroid cancer occurs in<1% of cases. ), resulting in higher concentrations of serum calcium being needed to inhibit PTH secretion. Subsequent PTH secretion induces renal phosphate excretion. Persistent hypercalcemia (usually asymptomatic) and often from an early age, normal to slightly elevated concentrations of PTH, hypocalciuria, and Hypermagnesemia occur. Renal function is normal, and nephrolithiasis is unusual. However, severe Secondary hyperparathyroidism occurs most commonly in advanced Tertiary hyperparathyroidism results in autonomous hypersecretion of PTH regardless of serum calcium concentration. Tertiary hyperparathyroidism generally occurs in patients with long-standing secondary hyperparathyroidism, as in patients with end-stage renal disease of several years’ duration. Cancer is a common cause of hypercalcemia, usually in hospitalized patients. Although there are several mechanisms, elevated serum calcium ultimately occurs as a result of bone resorption. (ie, hypercalcemia with no or minimal bone metastases) occurs most commonly with squamous cell carcinoma, Renal Cell Carcinoma , can be caused by metastatic solid tumors (eg, Breast Cancer , Vitamin D Toxicity can be caused by high concentrations of endogenous 1,25(OH)2D. Although serum concentrations are low in most patients with solid tumors, patients with Granulomatous disorders, such as Sarcoidosis , ), can result in hypercalcemia due to accelerated bone resorption. Hypercalcemia develops within days to weeks of onset of bed rest. Reversal of hypercalcemia occurs promptly on resumption of weight bearing. Young adults with several bone fractures and people with Paget Disease of Bone are particularly prone to hypercalcemia when at bed rest. Idiopathic infantile hypercalcemia (Williams syndrome—see table) is an extremely rare sporadic disorder with dysmorphic facial features, cardiovascular abnormalities, renovascular hypertension, and hypercalcemia. It leads to nephrocalcinosis in some patients. The cause of hypercalcemia is unknown. antacids for dyspepsia or to prevent Osteoporosis , resulting in hypercalcemia, 