parathormonu

Parathormone, also known as parathyroid hormone (PTH), is a hormone secreted by the parathyroid glands, four small glands located in the neck behind the thyroid gland. Its primary role is to regulate calcium and phosphate levels in the bloodstream. PTH acts on several target organs, including the bones, kidneys, and intestines, to achieve this regulation.

In the bones, PTH stimulates the release of calcium and phosphate into the blood by promoting the breakdown of bone tissue. In the kidneys, it increases the reabsorption of calcium from the urine, thereby conserving it in the body. Conversely, PTH decreases the reabsorption of phosphate in the kidneys. It also plays a crucial role in the activation of vitamin D in the kidneys. Activated vitamin D then enhances the absorption of calcium and phosphate from the intestines.

The secretion of PTH is tightly controlled by the level of calcium in the blood. When blood calcium levels drop, the parathyroid glands increase PTH secretion. Conversely, when blood calcium levels rise, PTH secretion is suppressed. This feedback mechanism ensures that blood calcium levels are maintained within a narrow, healthy range, which is essential for numerous bodily functions, including nerve signal transmission, muscle contraction, and blood clotting. Imbalances in PTH production or function can lead to conditions such as hyperparathyroidism or hypoparathyroidism, affecting calcium and phosphate homeostasis.