Calcium

99 percent of the calcium in the body is found in the bones as hydroxyapatite, making calcium the most common mineral in the body. The leftover calcium is spread throughout the body's tissues and extracellular fluids, where it is essential to numerous functions that support life. Calcium is involved in blood coagulation, neuromuscular conduction, excitability of skeletal and cardiac muscle, enzyme activation, and maintenance of cell membrane integrity and permeability, among other extraskeletal functions. Vitamin D, calcitonin, and parathyroid hormone (PTH) regulate serum calcium levels and, by extension, body content. Serum PTH or vitamin D increases are typically linked to hypercalcemia. Other neoplastic disorders such as multiple myeloma may also be associated with elevated serum calcium levels. In conditions including pancreatitis, nephrosis, and hypoparathyroidism, hypocalcemia may be seen