parahormone

Parathyroid hormone (PTH), also known as parathormone, is a hormone produced by the parathyroid glands that plays a crucial role in regulating serum calcium and phosphate concentrations. It is a protein hormone composed of 84 amino acids.12

PTH secretion is primarily controlled by the level of ionized calcium in the blood. When calcium levels drop, the parathyroid glands increase PTH secretion. Conversely, high calcium levels suppress PTH release.1

The actions of PTH work to increase serum calcium levels by:
* Mobilizing calcium from bone tissue by activating osteoclasts.1
* Stimulating the kidneys to reabsorb calcium from urine.1
* Promoting the production of calcitriol (active vitamin D) in the kidneys, which enhances calcium absorption from the gastrointestinal tract.1

PTH also lowers serum phosphate levels by increasing its excretion in the urine. This helps prevent the formation of insoluble calcium-phosphate complexes, further aiding in calcium regulation.12

Disruptions in PTH levels can lead to conditions like hyperparathyroidism (excess PTH) or hypoparathyroidism (insufficient PTH), each with distinct effects on calcium and phosphate balance and associated symptoms.12