Calcium hemostasis.
- Plasma calcium is comprised of 45% ionized free calcium, 40% protein-bound calcium, and 15% calcium associated with anions such as phosphate and citrate.
- The free calcium is the physiologically active form and is precisely regulated.
- Free hydrogen ions can displace free calcium ions from proteins.
- An increase in hydrogen ions due to acidosis will decrease the bound form of calcium, increasing free calcium and reducing the excitability of neurons.
- A decrease in hydrogen ions due to alkalosis will increase the bound form of calcium, reducing free calcium and increasing the excitability of neurons, which can lead to tetany.
Parathyroid hormone.
Source:
PTH is a peptide hormone released from the chief cells of the parathyroid gland. Its functions include:
- Increasing bone resorption of Ca and Po4.
- Enhancing kidney reabsorption of Ca2+ in the distal convoluted tubule.
- Increasing absorption of calcium in the intestine by boosting the production of activated vitamin D.