Which hormone is responsible for maintaining calcium balance in the bloodstream?

Parathyroid hormone plays a crucial role in maintaining calcium balance in the bloodstream. It is secreted by the parathyroid glands in response to low levels of calcium in the blood. This hormone increases calcium levels by stimulating the release of calcium from bones, enhancing calcium reabsorption in the kidneys, and promoting the activation of vitamin D, which in turn increases intestinal absorption of calcium.

Maintaining proper calcium levels is essential for various physiological functions, including muscle contractions, blood clotting, and nerve transmission. When calcium levels drop, parathyroid hormone works to restore them to normal ranges, illustrating its primary function in calcium homeostasis.