parathormont

Parathormone, also known as parathyroid hormone (PTH), is a peptide hormone produced and secreted by the parathyroid glands. These glands are small, typically four in number, located in the neck behind the thyroid gland. The primary role of parathormone is to regulate calcium and phosphate levels in the bloodstream.

The secretion of parathormone is primarily controlled by the concentration of calcium ions in the blood. When blood calcium levels drop below a certain threshold, the parathyroid glands are stimulated to release PTH. Conversely, when blood calcium levels rise, PTH secretion is suppressed.

Parathormone exerts its effects on several target organs, including the bones, kidneys, and intestines. In the bones, it promotes the release of calcium and phosphate into the bloodstream by stimulating osteoclasts, cells responsible for bone resorption. In the kidneys, PTH increases the reabsorption of calcium, thereby reducing its excretion in urine. It also decreases the reabsorption of phosphate, leading to increased phosphate excretion. Furthermore, PTH stimulates the kidneys to convert vitamin D into its active form, calcitriol. Calcitriol then enhances the absorption of calcium and phosphate from the intestines.

Through these actions, parathormone plays a crucial role in maintaining calcium homeostasis, which is essential for various physiological processes such as nerve function, muscle contraction, and blood clotting. Dysregulation of parathormone production or function can lead to various disorders, including hyperparathyroidism (excess PTH) and hypoparathyroidism (insufficient PTH), both of which can have significant health consequences.