Parathormone is a hormone produced by the parathyroids, structures connected to the thyroid gland located in the neck. The number of parathyroid glands varies from person to person, but in most cases there are four. The role of the parathormone is to maintain an adequately high concentration of calcium in the blood (serum calcium). It achieves this through two processes: by increasing intestinal absorption, stimulating its reabsorption into the kidneys, and increasing the amount of calcium released by bones. Parathormone production is activated as soon as serum calcium levels drop. Certain pathologies are responsible for increased secretion of parathormone, which lead to potentially serious hypercalcemia.