Kõrvalhormoonina

Kõrvalhormoonina, often translated as parathyroid hormone (PTH), is a peptide hormone produced by the parathyroid glands. These glands are located in the neck, close to or embedded within the thyroid gland. The primary role of PTH is to regulate calcium and phosphate levels in the bloodstream. It is a crucial component of the endocrine system, working to maintain homeostasis of these vital minerals.

When blood calcium levels drop too low, the parathyroid glands release PTH. This hormone then acts on several target organs to increase serum calcium. It stimulates the kidneys to reabsorb calcium from the urine, preventing its loss from the body. Simultaneously, PTH promotes the release of phosphate from the bones. In the kidneys, it also enhances the conversion of vitamin D to its active form, calcitriol. Calcitriol, in turn, increases the absorption of calcium and phosphate from the small intestine. This multi-pronged approach effectively raises blood calcium levels back to the normal range. Conversely, when blood calcium levels are high, PTH secretion is suppressed. This intricate feedback mechanism ensures that calcium levels are tightly controlled, which is essential for numerous physiological processes, including nerve function, muscle contraction, and blood clotting. Disorders affecting PTH production or function can lead to significant health problems related to calcium metabolism.