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Hyperparathyroidism

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Parathyroid glands

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Hyperparathyroidism

Definition:

Hyperparathyroidism is excessive production of parathyroid hormone by the parathyroid glands.

Causes, incidence, and risk factors:

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The parathyroid glands are located at the front and base of the neck around the thyroid gland. They produce parathyroid hormone, which regulates calcium, phosphorus, and magnesium levels within the blood and bone.

When calcium levels are too low, the body responds by increasing production of parathyroid hormone. This increase in parathyroid hormone causes more calcium to be taken from the bone and more calcium to be reabsorbed by the intestines and kidney. When the calcium level returns to normal, parathyroid hormone production slows down.

Excess parathyroid hormone can be produced for a variety of reasons. In some cases, parathyroid hormone is produced without regard to the calcium levels. This is called "primary hyperparathyroidism" and is caused by enlargement of one or more of the parathyroid glands. It is a common disorder affecting about 1 in 1,000 people. The high levels of calcium and parathyroid hormone affect several body systems, including the skeletal, gastrointestinal, renal, muscular, and central nervous system.

"Secondary hyperparathyroidism" is when the body produces extra parathyroid hormone because the calcium levels are too low. This is seen when vitamin D levels are low or when calcium is not absorbed from the intestines. Correcting the calcium level and the underlying problem will bring the parathyroid levels in the normal range.

If the parathyroid glands continue to produce too much parathyroid hormone even though the calcium level is back to normal, this is called "tertiary hyperthyroidism" and occurs especially in patients with kidney problems.