Familial isolated hyperparathyroidism

Familial isolated hyperparathyroidism is an inherited condition that is characterized by overactive parathyroid glands (hyperparathyroidism). The four parathyroid glands are located in the neck. They release a hormone called parathyroid hormone that regulates the amount of calcium in the blood. 

In people with familial isolated hyperparathyroidism, too much parathyroid hormone is produced, and levels of calcium in the blood become elevated (hypercalcemia). Hypercalcemia causes many of the common signs and symptoms of familial isolated hyperparathyroidism, such as kidney stones, nausea, vomiting, high blood pressure (hypertension), thinning of the bones (osteoporosis), weakness, and fatigue.

Many people with familial isolated hyperparathyroidism have one or more noncancerous (benign) tumors called adenomas. Typically, only one of the four parathyroid glands is affected, but sometimes more than one gland has an adenoma. Rarely, the tumor can become cancerous; this is called parathyroid carcinoma.

In some cases, familial isolated hyperparathyroidism may not be diagnosed until adulthood. Often, the first indication of the condition is elevated calcium levels that are identified during a routine blood test, even though the affected individual may not yet have signs or symptoms of hyperparathyroidism or hypercalcemia.