Multiple endocrine neoplasia (MEN) I is an inherited disorder in which one or more of the endocrine glands are overactive or form a tumor. Endocrine glands most commonly involved include:

• Adrenals
• Pancreas
• Parathyroid
• Pituitary
• 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 it affects men and women equally.

Risk factors for MEN I include:

• Family history of this disorder
• Pituitary tumor
• Zollinger-Ellison syndrome

Symptoms vary from person to person, and may include:

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

Signs may include:

• Coma (if low blood sugar is untreated)
• High blood calcium
• Kidney stones
• Low blood pressure
• Low blood sugar
• Pituitary problems (such as too much prolactin, a hormone that controls breast milk production)

Tests to diagnose MEN I may include:

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

Surgery to remove the diseased gland is the treatment of choice. A medication called bromocriptine may be used instead of surgery for pituitary tumors that release the hormone prolactin.

The parathyroid glands, which control calcium production, can be removed. However, it is difficult for the body to regulate calcium levels without these glands.

There is now effective medication to reduce the excess acid production caused by some tumors, and to reduce the risk of ulcers.

Hormone replacement therapy is given when glands are removed or do not produce enough hormones.

Pituitary and parathyroid tumors are usually noncancerous (benign), but some pancreatic tumors may become cancerous (malignant) and spread to the liver. These can lower life expectancy.

The symptoms of peptic ulcer disease, low blood sugar, excess calcium in the blood, and pituitary dysfunction usually respond well to treatment.

Recurrent tumors may develop.

Call your health care provider if you notice symptoms of MEN I.

Screening close relatives of people affected with this disorder is recommended.

Kronenberg HM. Polyglandular disorders. in: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 250.