Multiple endocrine neoplasia syndromes
The multiple endocrine neoplasia (MEN) syndromes are three related disordersaffecting the thyroid and other hormone producing (endocrine) glands of the body.
The three forms of MEN are MEN1 (Wermer's syndrome), MEN2A (Sipple syndrome),and MEN2B (previously known as MEN3). Each is a genetic condition that predisposes the carrier of the gene to excessive growth of cells (hyperplasia) andtumor formation in a number of endocrine glands.
MEN1 patients experience hyperplasia or tumors of several endocrine glands, including the parathyroids, the pancreas, and the pituitary. The most frequentsymptom of MEN1 is overgrowth of the parathyroid glands. This leads to an excess secretion of parathyroid hormone causing elevated blood calcium levels,kidney stones, weakened bones, and nervous system depression. Almost all MEN1patients show these symptoms by age 40.
Tumors of the pancreas are also common in MEN1. Excessive secretion of gastrin (a hormone secreted into the stomach to aid in digestion) by these tumors can cause upper gastrointestinal ulcers. The anterior pituitary and the adrenal glands can also be affected.
Patients with MEN2A and MEN2B experience two main symptoms, medullary thyroidcancer (MTC) and a tumor of the adrenal gland medulla known as pheochromocytoma. MTC is a slow-growing cancer, but one that can be cured in less than 50%of cases. Pheochromocytoma is usually a benign tumor that causes excessive secretion of adrenal hormones, which, in turn, can cause life-threatening hypertension and cardiac arrhythmia.
MEN2A patients have a tendency to develop tumors of the parathyroid gland. Although similar to MEN1, less than 20% of MEN2A patients will show parathyroidinvolvement. MEN2B patients show a variety of additional conditions: swollenlips; tumors of the mucous membranes of the eye, mouth, tongue, and nasal cavity; enlarged colon; and skeletal abnormalities. Symptoms develop early in life (often before five years of age) in cases of MEN2B and the tumors are more aggressive. MEN2A is about ten times more common than MEN2B.
All types of MEN are caused by inherited genetic defects in genes that control tumor suppression. A patient who inherits one defective copy of a tumor suppressor gene from either parent has a strong predisposition to the disease. For all types of MEN, the children of an affected individual have a 50% chanceof inheriting the defective gene.
MEN is diagnosed from clinical symptoms and testing for elevated hormone levels. For MEN1, the relevant hormone is parathyroid hormone. For both types ofMEN2, the greatest concern is development of medullary thyroid cancer. Numerous other hormone levels can be measured to assess the involvement of the various endocrine glands.
Before 1994, there was no way of definitively identifying which children or symptom-free adults who had inherited the MEN defective gene. Now genetic screening using DNA technology allows a positive distinction to be made between children who are and who are not at risk.
Children who are identified as carriers. The defective genes that cause MEN2Aor MEN2B can be offered total surgical removal of the thyroid gland (thyroidectomy) and synthetic thyroid hormone replacement as a way of preventing thedevelopment of thyroid cancer.
No single treatment is available for MEN. However, some of the symptoms caused by MEN can be treated. Surgical removal of some slow growing tumor is possible as is treatment of thyroid cancer by surgical removal of the thyroid. However, among doctors there is some disagreement about when thyroid removal should occur. After thyroidectomy, the patient receives replacement thyroid hormone either orally or by injection. Even when surgery is performed early, cancer may spread or metastasized to other parts of the body. chemotherapy and radiation therapy may not be effective in controlling its spread.
Diagnosed and treated early, patients with MEN may do very well. Untreated MEN may be fatal. Analysis of at-risk family members using genetic testing leads to earlier treatment and improved outcomes. There is no way to prevent thegenetic mutations that cause MEN.