Definition
- Calcium homeostasis is maintenance of plasma calcium within normal range by hormonal action on bone, kidney and intestine.
- Normal plasma calcium is 9 to 11 mg% (average 10 mg%); about 50% is ionized (biologically active).
Normal Values and Distribution
Normal calcium and phosphate values
Parameter
Plasma calcium
- Value
- 9 to 11 mg% (average 10 mg%)
Plasma phosphate
- Value
- 2.5 to 4.5 mg%
Plasma PTH
- Value
- 10 to 60 pg/mL
Plasma calcitonin
- Value
- 10 to 20 pg/mL
Total body calcium
- Value
- 1 to 1.5 kg
- About 40% of plasma calcium is protein-bound, about 10% complexed.
- Alkalosis decreases ionized calcium; acidosis increases it.
Distribution of body calcium
Compartment
Bone and teeth
- Share of total body calcium
- 99%
Intracellular fluid
- Share of total body calcium
- 0.9% (about 11 g)
Extracellular fluid
- Share of total body calcium
- 0.1% (about 1 g)