How Does Our Body Regulate Calcium?

Calcium levels are regulated by the parathyroid glands. That's all the parathyroid glands do! Through the secretion of parathyroid hormone (PTH), these four small glands regulate how much calcium is absorbed from our diet, how much calcium is secreted by our kidneys, and how much calcium is stored in our bones. We store many pounds of calcium in our bones, and it is readily available to the rest of the body at the request of the parathyroid glands. When one of the parathyroid glands is overactive (hyperparathyroidism) the parathyroid tumor makes too much PTH hormone which then causes our bones to release calcium constantly into the blood stream.

This causes the bones to lose their density and hardness (it is the calcium that makes them hard). Loss of calcium from bones is called osteoporosis. Bones which are osteoporotic are more likely to break! This picture shows a normal bone section on the bottom and a bone with osteoporosis on the top. The osteoporotic bone has bigger holes in it as a result of the calcium being dissolved and put into the blood stream (caused by excess parathyroid hormone, advanced age, and lack of estrogen in older females). The osteoporotic bone is not as strong and therefore, more susceptible to fractures. This continued dissolving of the central bone is what causes the bone pain so common to hyperparathyroidism. It is also what contributes to the weakening of the spinal column resulting in elderly persons walking "hunched over".
Our bones are at their strongest in our early 20's.

They stay at this level of strength for a number of years, but then begin to lose strength slowly when we are in our mid 30's. Once we hit mid-life, we all lose a little bone density, but this is most evident for women. Estrogens have a protective effect on bone density which becomes evident after menopause when women begin to lose calcium from their bones at a faster rate then men of the same age. That is one of the reasons most doctors feel that most post-menopausal women should be on some form of estrogen therapy.Now the problem becomes apparent. Overactive parathyroid glands secrete too much parathyroid hormone.

This causes calcium to leave the bones and go into the blood. The bones become osteoporotic and prone to fractures. The problem is amplified greatly in post-menopausal women since this process is ongoing already! This can also a big problem for people of all ages if it goes on for several years, making the bones weaker year after year.