paratüreoidhormooni

Paratüreoidhormooni, also known as parathyroid hormone (PTH), is a peptide hormone secreted by the parathyroid glands. These glands are located in the neck, behind the thyroid gland. PTH plays a critical role in regulating calcium and phosphate levels in the blood. Its primary function is to increase blood calcium concentration when it falls too low.

PTH exerts its effects through several mechanisms. It acts on the bones to stimulate the release of calcium from bone tissue into the bloodstream. In the kidneys, PTH promotes the reabsorption of calcium from the urine back into the blood, thereby reducing calcium loss. It also influences the kidneys to increase the excretion of phosphate, which helps to lower blood phosphate levels, and to convert vitamin D into its active form, calcitriol. Calcitriol, in turn, enhances the absorption of calcium from the intestines.

The secretion of PTH is tightly regulated by the level of calcium in the blood. When blood calcium levels are low, the parathyroid glands are stimulated to release more PTH. Conversely, when blood calcium levels are high, PTH secretion is suppressed. This feedback loop ensures that blood calcium levels are maintained within a narrow, healthy range, which is essential for numerous physiological processes, including nerve function, muscle contraction, and blood clotting. Imbalances in PTH levels can lead to conditions like hyperparathyroidism (excess PTH) or hypoparathyroidism (insufficient PTH), both of which can have significant health consequences.