Primary hyperparathyroidism is a hormonal problem which occurs when one or more of the parathyroid glands produces too much parathyroid hormone. When this occurs, blood calcium is elevated and bones may lose calcium. Surgical removal of the affected gland will cure the disorder. In secondary hyperparathyroidism, a problem such as kidney failure makes the body resistant to the action of parathyroid hormone. Hyperparathyroidism may cause no problems for many years or it may cause problems such as tiredness, weakness, muscle or bone pain, constipation, indigestion, kidney stones, or thinning of bones.
In 85 percent of people with this disorder, a benign tumour (adenoma) has formed on one of the parathyroid glands, causing it to become overactive. In most other cases, the excess hormone comes from two or more enlarged parathyroid glands, a condition called hyperplasia. Very rarely, hyperparathyroidism is caused by cancer of a parathyroid gland. The vast majority of cases occur in people with no family history of the disorder. Only about 3 to 5 percent of cases can be linked to an inherited problem. Familial endocrine neoplasia type I is one rare inherited syndrome that affects the parathyroids as well as the pancreas and the pituitary gland. Another rare genetic disorder, familial hypocalciuric hypercalcemia, is sometimes confused with typical hyperparathyroidism.
In the USA, about 100,000 people develop the disorder each year. Women outnumber men by 2 to 1, and risk increases with age. In women 60 years and older, 2 out of 1,000 will get hyperparathyroidism.