What is the role of exchangeable calcium in the pathogenesis of hypercalcemia?

Updated: Oct 03, 2018
  • Author: Mahendra Agraharkar, MD, MBBS, FACP, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

Only 1-2% of total body calcium is in the exchangeable form in circulation, and the rest forms part of the skeleton. Only one half of the exchangeable calcium is in the active ionized form with the remainder bound to albumin, globulin, and other inorganic molecules. Protein binding of calcium is influenced by pH with metabolic acidosis leading to increased ionized calcium from reduced protein binding, and alkalosis leading to reduced ionized calcium from increased protein binding. Because calcium binds to albumin and only the unbound (free or ionized) calcium is biologically active, the serum level must be adjusted for abnormal albumin levels.


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