Hyperparathyroidism is overactivity of the tiny glands in the neck
that are next to the thyroid gland (parathyroid glands). The parathyroid glands
release a substance called parathyroid hormone that helps control the amount of
calcium in the bloodstream.
When the parathyroid glands produce too much hormone, the amount of
calcium in the blood increases. The body removes calcium from the bones,
absorbs more calcium from the intestines, and releases less calcium into the
urine. This can result in constipation, nausea, vomiting, fatigue, and other
symptoms. It can also lead to kidney stones and weakening of the bones
Hyperparathyroidism may develop because of a tumor on the
parathyroid gland, as a side effect of treatment for other conditions (such as
Paget's disease), or for unknown reasons. Surgery may be needed to remove part
or all of the parathyroid glands.