The main functions of calcitonin, which is a naturally occurring hormone, are to help to regulate levels of calcium and phosphorus in the bodies of a variety of different animals. In its natural form, this hormone can help prevent the body from taking up calcium from the bones and from reabsorbing the mineral through the urinary tract. Both of these actions help to decrease the amount of calcium in the bloodstream of an animal. As a medical supplement, calcitonin can help prevent bone loss in patients with osteoporosis.
Mammals create calcitonin in the thyroid gland. Once it enters the bloodstream, one of its functions is to prevent the body from breaking down the calcium in the bones. This action helps to decrease the amount of calcium in an animal's bloodstream by lowering the amount of the mineral that moves from where it is stored in the bones to the blood. One of its other functions is to prevent the kidneys from taking up calcium, allowing it to pass out of the body through the urine instead.
Though this hormone has a significant effect on the amount of calcium in the blood of many animals, it does not appear that its role is as significant in humans. Human patients who have had the thyroid gland removed are still able to regulate the amount of calcium in their bloodstream through the use of other hormones.
In most cases, the presence of too much calcium in the blood stream signals the thyroid gland to release calcitonin to quickly lower the levels. Though increased levels of calcitonin in the blood can indicate a number of different medical disorders, the hormone does not appear to have a significant effect on the physiology of the human body. This makes it safe to use for the treatment of osteoporosis, as well as in other disorders related to hypercalcemia.
As a medical supplement, the most important of the functions of calcitonin is to help treat osteoporosis. This treatment is more commonly used for women than men because supplemental doses of the hormone testosterone can often help prevent bone loss in men. Men with normal levels of testosterone can be given calcitonin as a treatment, as can men who have not improved after treatment with testosterone. In women, calcitonin is usually only prescribed once treatment with biphosponates has proved ineffective.