Question

Explain how vitamin D interacts with the parathyroid hormone in activating vitamin D deficiency

Answer 1

The parathyroid glands are endocrine glands located in neck near thyroid glands (but no functional relation to). Their job is to secrete parathyroid hormone (PTH). PTH regulates serum calcium and phosphate, which in return regulate PTH. Kidney produces vitamin D’s active form, which is called 1,25(OH)₂D. How much 1,25(OH)₂D kidney decides to produce depends on how much PTH and calcium are in the body.

This is how it all happens:

When calcium level in blood is low, parathyroid starts secreting PTH. PTH starts pulling calcium from bones and into blood. PTH also infuences kidneys to start making more 1,25(OH)₂D. Vitamin D is stored in body called 25(OH)D that are ready for the kidney to produce 1,25(OH)₂D when needed and vitamin D defficiency in body is filled up.

When the kidney starts producing 1,25(OH)₂D, it helps the gut absorb more calcium than usual. When 1,25(OH)₂D increases and helps body get to the right calcium balance, parathyroid stops making so much PTH, and stops pulling calcium from bones.

On the other hand, when calcium in the blood is high, parathyroid won’t release much PTH at all. The amount of calcium in blood tells parathyroid not to release any PTH, and in turn, PTH doesn’t tell kidney to produce more 1,25(OH)₂D. So the body stops absorbing too much calcium and its blood calcium drops down.

This interaction between calcium, parathyroid and vitamin D is happening constantly; 1,25(OH)₂D and PTH always adjusting to make sure the body has the right calcium balance.