What causes hyperparathyroidism?

The parathyroid glands are round, pea sized glands in the neck that produce parathyroid hormone. Parathyroid hormone is essential for regulating the amount of calcium and phosphorus in the body. Both calcium and phosphorus are essential for the function of every cell in the body.  When the phosphorus or calcium blood levels rise or fall out of the normal range, a multitude of consequences occur, producing the symptoms of parathyroid disease.

Normally these glands are regulated so that they only produce the proper amount of hormone. For example, as the calcium level in blood increases, the parathyroid glands stop releasing parathyroid hormone. When the calcium level in blood decreases past a certain point, the parathyroid glands make more parathyroid hormone to bring the calcium level back to the normal range. In some people, the glands can become abnormal and loose the ability to regulate how much hormone they release. Hyperparathyroidism is a condition where the parathyroid glands produce too much parathyroid hormone. There are several types of hyperparathyroidism, each with different causes.

Primary hyperparathyroidism describes a condition where the one or more of the parathyroid glands produces too much parathyroid hormone. A parathyroid adenoma is a benign (non-cancerous) tumor of a parathyroid gland. Another condition is hyperplasia (increased growth) of all the parathyroid glands.  Parathyroid cancer occurs very rarely. In all 3 of these diseases, the abnormal parathyroid gland or glands do not respond to feedback from the body telling the gland to stop producing parathyroid hormone. Therefore, the gland keeps producing parathyroid hormone, even when the calcium blood level is abnormally high.

Secondary hyperparathyroidism occurs when the calcium levels are chronically low. When the calcium blood level is too low, the body tells the parathyroid glands to produce extra parathyroid hormone. Kidney disease may cause a loss of calcium in the urine. There are also some conditions which decrease the intestine’s ability to absorb calcium into the body. In some cases, even after the calcium levels are corrected by treating the underlying condition, the parathyroid glands continue to secrete high levels of parathyroid hormone, resulting in an elevation of calcium blood levels. This condition is called tertiary hyperparathyroidism.

There are no known risk factors for parathyroid disease. Nothing a person does or does not do will cause or prevent parathyroid disease.

Hypoparathyroidism is a condition that occurs when too little parathyroid hormone is produced. This condition is almost always due to surgical removal of the parathyroid glands.