Parathüroidnääred

Parathüroidnääred are small endocrine glands located in the neck, typically situated behind or attached to the thyroid gland. Humans usually have four parathyroid glands, two on each side, but variations in number and location can occur. These glands are crucial for regulating calcium and phosphate levels in the blood.

The primary hormone produced by the parathyroid glands is parathyroid hormone (PTH). PTH plays a vital role in maintaining calcium homeostasis. When blood calcium levels drop too low, the parathyroid glands release PTH. This hormone acts on several targets to increase calcium levels. It stimulates the bones to release stored calcium into the bloodstream. It also signals the kidneys to reabsorb more calcium from the urine, reducing its excretion. Furthermore, PTH promotes the activation of vitamin D in the kidneys, which in turn enhances calcium absorption from the intestines.

Conversely, when blood calcium levels are sufficiently high, PTH secretion is suppressed, helping to prevent hypercalcemia. The precise regulation of calcium by PTH is essential for numerous bodily functions, including nerve transmission, muscle contraction, and blood clotting. Disorders of the parathyroid glands, such as hyperparathyroidism (overactive glands) or hypoparathyroidism (underactive glands), can lead to significant health problems due to imbalances in calcium levels.