Multiple endocrine neoplasia (MEN) I is disorder passed down through families (inherited) in which one or more of the endocrine glands have too much tissue or form a tumor. Endocrine glands include the parathyroid, pancreas, pituitary, adrenals, or thyroid.

MEN I is caused by a defect in a gene called RET. The condition causes tumors of various glands to appear in the same person, but not necessarily at the same time. The disorder may occur at any age, and affects men and women equally.

Most persons with MEN I seek medical treatment for a severe form of peptic ulcer disease caused by a tumor in the pancreas and symptoms related to low blood sugar, high blood calcium, kidney stones, or pituitary problems (such as headache).

Risk factors for MEN I include a family history of this disorder, a previous pituitary tumor, and a history of Zollinger-Ellison syndrome.

Symptoms vary greatly from person to person. They may include:

• Abdominal pain
• Burning, aching, or hunger discomfort in the upper abdomen or lower chest that is relieved by antacids, milk, or food
• Black, tarry stools
• Nausea and vomiting
• Bloated feeling after meals
• Weakness
• Headache
• Vision problems
• Loss of coordination
• Anxiety
• Mental changes or confusion
• Coma (if hypoglycemia is untreated)
• Loss of appetite
• Muscle pain
• Fatigue
• Sensitivity to the cold
• Unintentional weight loss
• Low blood pressure
• Loss of underarm or pubic hair
• In women, cessation of menses, infertility, or failure to produce breast milk
• In men, decreased sexual interest, loss of body or facial hair

Tests to diagnose MEN I may include:

• MRI of abdomen
• MRI of the head
• CT of abdomen
• Cranial CT scan
• Parathyroid biopsy
• Insulin test
• Fasting blood sugar
• Serum glucagon
• Serum gastrin
• Serum calcium
• Serum parathyroid hormone
• Serum prolactin
• Serum thyroid stimulating hormone (rarely used)
• Cortisol
• Serum adrenocorticotropic hormone
• Serum luteinizing hormone
• Serum follicle stimulating hormone