Question

Discuss the phosphate regulation mechanism

Answer 1

Answer: Phosphate regulation is also known as Phosphate homeostasis. Phosphate is an essential mineral required for the bones and teeth building and repair, muscle contraction and better nerve functioning. Phosphorous and calcium serum level are interrelated, and their regulation mechanism depends upon each other.

Phosphorous is absorbed by cellular and intracellular pathways in intestine and its serum concentration is regulated by parathyroid hormone (PTH), bones and kidneys.

PTH secretion by parathyroid gland is regulated by serum calcium levels as well as phosphorous levels. It stimulates phosphate excretion through the kidneys also it regulates calcitriol synthesis. The Kidneys help by filtering the excess amount present in blood and pass it out of the body through urine. Continuous excretion through kidneys leads to lower serum phosphate levels and calcitriol that results in inhibition of PTH production.

In the bone, along with PTH, fibroblast growth factor-23 (FGF-23) is also responsible for calcium phosphorus regulation. FGF23 is regulated by bone signaling mechanism (negatively) and systemic factors (positively). PTH stimulates FGF-23 production leading to increased release of calcium and phosphate by bones, increased gut absorption of calcium and phosphate, and increase in renal calcium absorption following an increase in bone resorption. In the kidney, FGF-23 decreases phosphate reabsorption and decreases the synthesis of 1,25-dihydroxyvitamin D3. In the parathyroid glands FGF23 suppresses the production and secretion of PTH.