Secondary hyperparathyroidisrn are seen in all except aEUR'

Osteoporosis Secondary hyperparathyroidism :? Secondary hyperparathyroidism is seen when there is some resistance to metabolic actions of parathyroid hormone; so inspite of increase in the level of parathyroid hormone, the serum calcium level is not increased. Renal failure is by far the most common cause of secondary hyper- parathyroidismQ. Chronic renal failure results in phosphate retention and hyper- phosphatemia Hyperphosphatemia in turn induces secondary hyperparathyroi- disco because phosphate regulates PTH secretion. Inspite of the increased PTH, serum calcium remains low or normal because the damaged kidneys are not able to generate the active metabolite of vitamin D, which is 1,25 dihydroxy cholecalci- ferol. Due to renal failure, the enzyme renal hydroxylase is damaged and this prevents the formation 1,25(011)2 cholecalciferol. Secondary hyperparathyroidism Vitamin D deficiency or impaired 1,25 (OH)2 D production / action - Nutritional vitamin D deficiency (poor intake or absorption) - Renal insufficiency with impaired 1,25 (OH)2 D production - Vitamin D resistance including receptor defects Parathyroid hormone resistance syndrome PTH receptor mutations - Pseudohypoparathyroidism Drugs - Calcium chelators - Inhibitors of bone resorption (biphosphonates, plicamycin - Altered vitamin D metabolism (phenytoin, ketoconazole) Miscellaneous causes - Acute pancreatitis - Acute rhabdomyolysis - Hungry bone syndrome after parathyroidectomy - Osteoblastic metastases with marked stimulation of bone formation (prostate cancer)