Paratüroidhormooni

Paratüroidhormooni, also known as PTH, is a hormone produced by the parathyroid glands. These four small glands are located in the neck, near the thyroid gland. PTH plays a crucial role in regulating calcium levels in the blood. It works by increasing the concentration of calcium in the extracellular fluid, primarily through its effects on bone, kidneys, and the intestine.

When blood calcium levels drop too low, the parathyroid glands release PTH. In the bones, PTH stimulates osteoclasts, which are cells that break down bone tissue, releasing calcium into the bloodstream. In the kidneys, PTH increases the reabsorption of calcium from the urine, preventing its loss from the body. It also promotes the production of calcitriol, the active form of vitamin D, which in turn enhances calcium absorption from the intestines. Conversely, when blood calcium levels are too high, PTH secretion is suppressed. This intricate feedback loop ensures that calcium homeostasis is maintained, which is essential for numerous bodily functions, including nerve impulse transmission, muscle contraction, and blood clotting.