Disorders of Calcium Metabolism: Hypocalcemia and Hypercalcemia.

Calcium (Ca) is a divalent cation that plays a critical role in numerous body functions such as skeletal mineralization, signal transduction, nerve conduction, muscle contraction, and blood coagulation. Ca metabolism is linked to magnesium (Mg) and phosphate metabolism. Cahomeostasis is dependent on intestinal absorption, bone turnover, and renal reabsorption. The hormonal regulators of these processes are the parathyroid hormone (PTH), calcitriol {1,25-dihydroxyvitamin D [1,25(OH)D]}, and serum ionized Ca. Cloning of the Ca-sensing receptor (CaSR) has greatly advanced the understanding of Ca metabolism. Disorders of Ca metabolism are easily recognized because Ca is included in routine chemistry panels. Measurement of ionized Ca is the preferred way to ascertain the diagnosis of hypocalcemia and hypercalcemia.