Multiple endocrine neoplasia type 1 (MEN1) is characterized by endocrine tumors, particularly in the parathyroid glands, anterior pituitary, and pancreatic islet cells. Primary tumors may be found in more than one endocrine organ and/or multiple tumors may be found in the same organ. MEN1-associated endocrine tumors cause an array of clinical
and biochemical manifestations secondary to hormone hypersecretion: hyperparathyroidism (the most frequent MEN1-symptom with potential effects on the central nervous system (CNS), hypercalcemia, gastrointestinal, renal cardiovascular, and skeletal involvement), hypercortisolism, gigantism and acromegaly, prolactinoma (with associated oligomenorrhea, amenorrhea, and galactorrhea in females and sexual dysfunction in males), gastrinoma, and insulinoma. Non-endocrine tumors also are common and can include facial angiofibromas and collagenomas of the skin, lipomas, meningioma and ependymoma of the CNS, and leiomyomas. MEN1 is caused by mutations in the menin gene (MEN1), which are highly penetrant. Approximately 50% of MEN1 mutation carriers are symptomatic by age 20 and 95% are symptomatic by the age of 40.