Landmark Discoveries in Calcium Metabolism Review of Literature

Calcium metabolism plays an integral role in maintaining homeostasis. Over 99% of the calcium present normally in the adult human body resides in the skeleton, where it provides mechanical stability and serves as a reservoir sometimes needed to maintain extracellular fluid (ECF) calcium concentration. Ionized calcium in the ECF must be maintained within a narrow range because of the critical role calcium plays in a wide array of cellular functions, especially in the neuromuscular activity, secretion, and signal transduction. Intracellular cytosolic free calcium levels are ~100nmol/L and are 10,000-fold lower than ionized calcium concentrations in the blood and ECF (1.1-1.3mmol/L). Cytosolic calcium does not play the structural role played by extracellular calcium; instead, it serves a signaling function. The steep chemical gradient of calcium from outside to inside the cell promotes rapid calcium influx through various membrane calcium channels that can be activated by hormones, metabolites, or neurotransmitters, swiftly changing cellular function. In blood, total calcium concentrations normally 2.2-2.6mM (8.5-10.5mg/dL), of which ~50% is ionized [1].