Calcium is a functionally important ion and coenzyme in most all of the body systems. Besides its structural role in bone, calcium is involved in muscle contraction, the blood coagulation system, enzyme activity, nerve impulse transmission, hormone release and membrane permeability.I-3 Calcium metabolism is regulated primarily by parathyroid hormone (PTH), calcitonin (CT), and vitamin D (1,25-dihydroxycholecalciferol). The release of these hormones is controlled by the concentration of calcium in the plasma. Exact regulation of calcium in extracellular fluid is necessary to maintain normal body function.