Hyperparathyroidism is the result of an overproduction of a hormone called parathyroid hormone (or PTH) from the parathyroid glands. The parathyroid glands are four small glands that surround the thyroid and are found in the anterior part of the lower neck. They are about the size of a pea. Occasionally, they may be in different locations because of the way the glands develop, but the location (embedded in the thyroid for example) does not itself affect the function of the gland.
The main job of the parathyroid glands is to regulate calcium levels in the body. If calcium levels are low, PTH levels increase; whereas if calcium is high, PTH levels are reduced. Calcium is a mineral that is important in the regulation and processes of many body functions including bone formation, hormone release, and muscle contraction, as well as nerve and brain function.
A condition referred to as hypocalciuric hypercalcemia, is often confused with hyperparathyroidism as it involves calcium production. In this condition, the kidneys do not excrete the normal amounts of calcium. It is not a severe disorder, is not a disorder of the thyroid, and is not the same as hyperparathyroidism.
The thyroid's production of PTH regulates calcium by influencing absorption in the GI tract, excretion in the urine, and release from the bones. If too much PTH is released, calcium regulation is disrupted, and calcium levels in the blood increase through the mechanisms noted above.
There are three main types of hyperparathyroidism. Primary hyperparathyroidism means the underlying problem starts in the parathyroid glands. Secondary and tertiary hyperparathyroidism means that another disease in the body has caused the parathyroid glands to be overactive. In secondary hyperparathyroidism, there is an signal to the gland to produce more parathyroid hormone (for example, a low vitamin D level). In tertiary hyperparathyroidism, the glands continue to over-secrete parathyroid hormone even though the signal is gone. These conditions may be seen in kidney disease.
This article focuses on primary hyperparathyroidism.
Medically Reviewed by a Doctor on 6/23/2014
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