QS Study

State the Mechanism of Parathyroid Hormone Secretion

Parathyroid hormone regulates the body’s calcium levels. It controls the calcium in our blood and bones. The thyroid gland regulates the body’s metabolism and has no effect on calcium levels while parathyroid glands control calcium levels and have no consequence on metabolism.

Parathyroid hormone provides a powerful mechanism for controlling ECF Ca++ and phosphate level.

Fig.: Mechanism Action of PTH

Mechanism of action of PTH:

PTH maintains calcium homeostasis through its effects on target tissues, bone, and kidney. Regulation of PTH secretion relevant to the management of secondary hyperparathyroidism in chronic kidney disease. PTH functions in calcium homeostasis, the regulation of ECF calcium concentration. The effects of PTH in the body are to raise the ECF calcium concentration.

Parathormone has three receptors –

(1) hPTH/PTHrP → also binds with parathyroid-related protein,

(2) PTH2 – found in the brain, the placenta does not bind PTHrP),

(3) CPTH – Reacts with carboxyl terminal of PTH.

H-R → Activation of adenylyl cyclone →↑ cAMP Action of PTH.