Multiple Endocrine Neoplasia I (MEN I)

Multiple endocrine neoplasia I or MEN I is a genetic disorder that causes specific tumours in the endocrine glands and in the duodenum. It is also known as Wermer's syndrome after one of the doctors that first identified the disease. The disease affects both genders equally and occurs in one out of 30,000 live births. MEN I affects the endocrine glands, which are the glands that release hormones into the body to affect other areas of the body. Hormones are specific chemicals that bind to cells and affect certain cells of the body.

In MEN I, the affected glands include the pancreas, the parathyroid glands and the pituitary gland. The tumours that form often form at exactly the same time, making the diagnosis easier. The glands form tumours but do not tend to be overactive.

When the parathyroid glands are involved, they form hyperparathyroidism. The parathyroid glands are four glands buried beneath and within the thyroid gland. In MEN I, the disease forms parathyroid adenomas, releasing too much parathyroid hormone (PTH) into the bloodstream. This messes with the calcium in the blood and with the bones that receive the calcium. There is too much calcium in the blood when a person has MEN I because of adenomas of all four parathyroid glands. The glands are not cancerous-just overactive. The bones can lose calcium and can become weak. Most people with hyperparathyroidism from MEN I get the disease before the age of 50 but some can get it before the age of 20. Symptoms include fatigue, muscle or bony pain, weakness, constipation, kidney stones or indigestion. Osteoporosis can also come from this disorder. Treatment includes surgery to remove at least three if not all of the glands making up the parathyroid gland.

The pancreas is also affected by MEN I. The pancreas releases insulin, glucagon, somatostatin, vasoactive intestinal peptide and gastrin. In MEN I, it is the gastrin that is over secreted in a condition known as a gastrinoma of the pancreas. Gastrin causes too much stomach acid to be secreted and serious diarrheal symptoms. The person can develop ulcers of the stomach quite easily in an illness called Zollinger-Ellison syndrome. It is difficult to treat the ulcers caused by this syndrome. There are often many gastrinomas in the pancreas at the same time, making surgical correction of this aspect of the disorder very difficult. The treatment revolves around taking acid pump inhibitors like Prilosec in order to block the excess gastrin production. Insulinomas can also be a part of MEN I and the person often has low blood sugar or hypoglycaemia. About ten percent of people with MEN I go on to develop insulinomas. Even less common are gastrinomas which lead to diabetes mellitus. Tumours that secrete ACTH can also come out of the pancreas in MEN I. Rarely gonadotropin-releasing hormone tumours can be a problem in cases of MEN I.

The pituitary gland is a small gland at the base of the brain. It produces multiple hormones used in reproduction, metabolism and other body functions. About a fourth of patients develop prolactinomas, which secrete prolactin that affects milk production by the mammary glands. There can be an excessive amount of breast milk produced and it can interfere with fertility in both men and women.

There may need to be no treatment for prolactinomas except for dopamine agonist medication that can shrink the tumour and can result in a lower production of prolactin.

Less commonly, MEN I can cause tumours that secrete ACTH, which stimulates the adrenal glands to make too much cortisol. This results in pituitary-induced Cushing's syndrome. Other pituitary tumours less common in MEN I include growth hormone tumours.

The treatment of MEN I is directed at slowing the production of the various hormones secreted in the disease. It can be very difficult to treat, especially if there is no antidote for the hormone secreted. The glands can be surgically removed, with the exception of the pituitary gland.