1. 99% of the body calcium is in the skeleton.
2. Only 1% is circulation and only half of this is free calcium (ionized Ca++).
3. This only is physiologically active.
4. The remaining is bound to albumin, immunoglobulin or loosely complexed with phosphate citrate, sulfate and other anions.
5. The normal total extracellular calcium 8.5mg/dL to 10.5 mg/dL.
6. Alterations in blood pH can alter ionized calcium: acidosis decreases Ca2+/albumin binding; alkalosis increases it.
Calcium Homeostasis
Parathyroid Hormone
1,25 DHC or Vitamin D3
Calcitonin
Calcium Metabolism
