About two thirds of the people with type I disease develop pituitary gland tumors. About 25 percent of these tumors produce the hormone prolactin, leading to menstrual abnormalities in women and impotence in men. Another 25 percent produce growth hormone, leading to acromegaly. A very small percentage of pituitary tumors produce corticotropin, leading to high levels of corticosteroid hormones and Cushing's syndrome. Nearly 25 percent appear to produce no hormones at all.
Some pituitary tumors cause headaches, impaired vision, and decreased pituitary gland function.
Some people with type I disease develop thyroid and adrenal gland tumors. A very small percentage develop carcinoid tumors. Almost everyone with type IIA disease develops medullary thyroid cancer. About 50 percent develop pheochromocytomas, which usually raise blood pressure because of the epinephrine and other substances they produce. The high blood pressure may be intermittent or constant and is often very severe.