Paratüroidnäärmete

Paratüroidnäärmete, also known as the parathyroid glands, are four small endocrine glands located in the neck, typically behind the thyroid gland. These glands are crucial for regulating calcium levels in the body. Each parathyroid gland is about the size of a grain of rice. Despite their proximity to the thyroid, they are functionally distinct and have a separate origin embryologically.

The primary function of the parathyroid glands is the secretion of 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 then acts on several target organs, including the bones, kidneys, and intestines. In the bones, PTH stimulates osteoclasts to break down bone tissue, releasing calcium into the bloodstream. In the kidneys, PTH increases the reabsorption of calcium from the urine back into the blood and promotes the excretion of phosphate. It also stimulates the activation of vitamin D in the kidneys, which in turn enhances calcium absorption from the digestive tract.

Conversely, when blood calcium levels are too high, PTH secretion is suppressed, leading to a decrease in these bone resorption and kidney reabsorption processes. This delicate balance is essential for numerous bodily functions, including nerve transmission, muscle contraction, blood clotting, and bone health. Imbalances in parathyroid function can lead to various medical conditions, such as hyperparathyroidism (overactive glands leading to high calcium) or hypoparathyroidism (underactive glands leading to low calcium).