MSK 7 – Simplifying Calcium and Phosphate Regulation

Calcium and Phosphate regulation is complicated as it ties the GI, kidneys and bones together.
Join us as we go through how PTH, Calcitriol regulate calcium and phosphate.

Calcium and Phosphate regulation

Calcium and Phosphate regulation

In short:

PTH: increases [calcium], decreases [phosphate]
Calcitriol: increases [calcium], increases [phosphate]

FOUR actions of Parathyroid Hormone(PTH):

1. Increase bone resorption leading to rise in calcium and phosphate.
2. Phosphate is filtered in the kidney and it’s resorption is blocked by PTH. This leads to an overall drop in phosphate levels.
3. Calcium is filtered in the kidneys but the resorption is increased by PTH. This leads to an overall increase in calcium concentration.
4. PTH increases Calcitriol (activated Vit D) production in the kidneys. This indirectly increases calcium absorption from the intestines.

FOUR actions of Calcitriol (activated vitamin D)

1. Increases bone resorption causing a rise in calcium and phosphate levels.
2. Calcitriol INCREASES the reabsorption of phosphate in the kidneys.
3. Calcitriol increases the reabsorption of calcium in the kidneys.
4. Calcitriol acts DIRECTLY on the intestines to increase calcium absorption from diet.

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