TY - CHAP M1 - Book, Section TI - Calcium, Phosphorus, and Magnesium Metabolism: Normal Mineral Homeostasis A1 - Merchant, Nadia A1 - Root, Allan A1 - Lin, Yuezhen A1 - Bacino, Carlos A. A2 - Kline, Mark W. PY - 2018 T2 - Rudolph's Pediatrics, 23e AB - The serum calcium concentration is tightly regulated by the kidney, intestinal tract, and bone through multiple hormonal pathways. Over 98% of total body calcium is deposited in bone along with phosphate as hydroxyapatite [Ca10(PO4)10(OH)2]. About 1% of calcium circulates in the plasma in 3 different forms: about 50% is a physiologically active form as ionized free calcium (Ca2+), about 40% of calcium is inert as it is bound to albumin and globulins, and about 10% is complexed with citrate, sulfate, or phosphate. Total plasma calcium measures free and bound calcium. Measuring only total plasma calcium concentration is usually sufficient for clinical purposes since its values correlate with free Ca2+ levels. However, in the presence of hypoalbuminemia, acid-base disorders, or chronic kidney disease, the serum calcium and Ca2+ levels may or may not correlate. Thus, acidosis decreases calcium binding to albumin, thus causing increased free Ca2+ concentrations; alkalosis increases calcium binding to albumin thus having the opposite effect. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/10/11 UR - accesspediatrics.mhmedical.com/content.aspx?aid=1182921217 ER -