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Abstract
Calcium is a divalent cation found primarily in the extracellular fluid. Circulating calcium protein bound (40%), chelated (10%) and ionized fractions (50%); only the ionized fraction is physiologically active. Calcium is essential for excitation contraction coupling, ciliary movement, mitosis, neurotransmitter release, enzyme secretion, hormonal secretion and cellular metabolism. In addition, it forms structural component of bone and cell membranes. Calcium is regulated mainly by parathyroid hormone, calcitonin and calcitriol as well as parathyroid hormone related peptide, glucocorticoids, growth hormone and thyroid hormone (Ganong, 2005).
Abnormalities in serum calcium concentration may have profound effects on neurological, gastrointestinal, and renal function. Maintenance of the normal serum calcium is a result of tightly regulated ion transport by the kidney, intestinal tract and bone mediated by calcaemic hormones, especially parathyroid hormone and 1,25 dihydroxyvitamin D3. Abnormalities in calcium transport that result in uncompensated influx into or efflux from the extracellular fluid will result in hypercalcaemia or hypocalcaemia, respectively. When possible the biologically important ionized calcium concentration should be measured. A variety of common disorders are responsible for abnormalities in the serum calcium. Treatment of both hypercalcaemia and hypocalcaemia is dependent on the underlying disorder, the magnitude of the deviation of the serum calcium, and the severity of symptom (Bushinsky and Monk, 1998).