Calcium

Calcium

Calcium is the fifth substance and most abundant cation in the body and 99% of this amount is stored as calcium pyrophosphate in hydroxyapatite crystals in the skeleton. About half of calcium is bound to plasma proteins (such as albumin) and is metabolically inactive and the rest are either complex calcium (bound to ions such as oxalate and citrate) or ionized calcium, which is physiologically active and its amount changes with the pH and concentration of serum proteins, so that acidosis reduces ionized calcium and increases alkalosis because ionized calcium and hydrogen ions compete to bind negative charge of protein molecules at the albumin binding site. Calcium plays an important role in maintaining the natural tone and excitability of skeletal and cardiac muscles, clotting process, DNA and RNA synthesis, plasma buffering capacity and enzyme activity and bone formation. There is an inverse relationship between Ca and P. Hypercalcemia is almost always corresponds to hypophosphatemia and conversely. Hypercalcemia is observed in overdose of vitamin D, sarcoidosis, kidney transplantation, hyperthyroidism and hypocalcemia in hypothyroidism, congenital resistance to parathyroid hormone, magnesium deficiency, renal failure (especially in dialysis patients), malnutrition, alcohol abuse, high phosphorous, surgery,burns, hemodialysis and acute pancreatitis. Measurement of serum calcium levels is used to evaluation blood serum calcium levels, monitor cancer patients, kidney patients, multiple myeloma and patients treated with calcium supplements and evaluate the effectiveness of treatment.