Abnormalities in Calcium Homeostasis
Calcium plays an important role in a number of physiological processes as diverse as bone formation and turnover, neuronal cell excitability, muscle contractility, and blood clotting. Significant shifts in serum calcium concentration have adverse effects
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Ruben Diaz
Abstract
Calcium plays an important role in a number of physiological processes as diverse as bone formation and turnover, neuronal cell excitability, muscle contractility, and blood clotting. Significant shifts in serum calcium concentration have adverse effects on these physiological functions. In children, maintenance of adequate calcium balance is particularly important since bone deposition and growth is closely linked to the availability of calcium. Higher organisms have developed mechanisms to regulate the extracellular concentration of calcium, normally affected by intermittent changes in calcium absorption in the gut, continuous mineral bone turnover, and calcium losses in the urine. Extracellular calcium levels are set within a very narrow range by the concerted action of several regulatory “calciotropic” hormones on calcium handling by the gastrointestinal tract, bone, and kidney. The abnormal function of calciotropic hormones or the failure of any of these organs to handle calcium properly can cause either hypo-or hypercalcemia. Keywords
Calcium • Hypercalcemia • Hypocalcemia • Vitamin D • Parathyroid hormone • Phosphate
Calcium plays an important role in a number of physiological processes as diverse as bone formation and turnover, neuronal cell excitability, muscle contractility, and blood clotting. Significant shifts in serum calcium concentration R. Diaz, M.D., Ph.D. (*) Endocrine Division, Saint John of God Hospital, Passeig Sant Joan de Deu 2, Esplugues de Llobregat 08950, Barcelona, Spain e-mail: [email protected]
have adverse effects on these physiological functions. In children, maintenance of adequate calcium balance is particularly important since bone deposition and growth is closely linked to the availability of calcium. Higher organisms have developed mechanisms to regulate the extracellular concentration of calcium, normally affected by intermittent changes in calcium absorption in the gut, continuous mineral bone turnover, and calcium losses in the urine.
S. Radovick and M.H. MacGillivray (eds.), Pediatric Endocrinology: A Practical Clinical Guide, Second Edition, Contemporary Endocrinology, DOI 10.1007/978-1-60761-395-4_20, © Springer Science+Business Media New York 2013
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Extracellular calcium levels are set within a very narrow range by the concerted action of several regulatory “calciotropic” hormones on calcium handling by the gastrointestinal tract, bone, and kidney. The abnormal function of calciotropic hormones or the failure of any of these organs to handle calcium properly can cause either hypoor hypercalcemia. Calcium is among the most abundant mineral ions in the body. Greater than 98% of total calcium is present as mineral salts in bone but can be mobilized as part of a continuous exchange of calcium between bone and the extracellular compartment during bone remodeling. The remaining fraction of calcium is distributed between the intracellular and extracellular compartments. Calcium in serum exists in three forms: (1) a protein-bound fraction (
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