Hypercalcemia

Excerpt

Calcium is the most abundant cation found in the human body and plays an integral role in neural transmission, enzyme activity, myocardial function, coagulation, and other cellular functions. Most of the calcium is found in the bones as calcium phosphate while a small percentage is found in the cells and extracellular fluids. In the serum, about 45% of calcium is bound to proteins, 45% exists as the active form of free or ionized calcium, and 10% is bound to anions. Normal calcium levels are approximately 8.9 to 10.1 mg/dL but this number can vary based on which laboratory is used. Serum calcium levels fluctuate based on serum albumin levels, as a large percentage of calcium is bound to albumin. Therefore, calcium levels must be adjusted based on albumin levels. Hydrogen ions also bind to circulating albumin, so both acidosis and alkalosis can affect serum calcium levels. For example, increased hydrogen ions in acidosis take up additional binding sites on albumin and, therefore, lead to increased free calcium levels. For this reason, calcium levels should also be adjusted for serum pH.