Multiple Endocrine Neoplasia, Type 1 (MEN 1)

Multiple endocrine neoplasia (MEN) is a rare genetic condition characterized by multiple tumors and/or cancer that affect specific endocrine system glands and tissues.

There are two main types of the condition:

• Multiple endocrine neoplasia (MEN) type 1: This is a genetic condition in which multiple tumors affect different aspects of your endocrine system.
• Multiple endocrine neoplasia type 2 (MEN2): This is a genetic polyglandular (multiple glands) cancer syndrome. People with MEN2 will develop medullary thyroid cancer (carcinoma) and have an increased risk of developing other tumors that affect other glands in the endocrine system.

Other names for multiple endocrine neoplasia type 1 include:

• MEN-1.
• MEN-1 syndrome.
• Multiple endocrine adenomatosis.
• Wermer’s syndrome.

Other names for multiple endocrine neoplasia type 2 include:

• MEN-2.
• MEN2 syndrome.
• Sipple syndrome.

What is the endocrine system?

Your endocrine system is a network of several glands and organs that create and secrete (release) hormones.

Hormones are chemicals that coordinate different functions in your body by carrying messages through your blood to your organs, skin, muscles and other tissues. These signals tell your body what to do and when to do it.

The following organs and glands make up your endocrine system and produce and release hormones:

• Hypothalamus: This gland is located on the undersurface of your brain and controls aspects of your endocrine system.
• Pituitary gland: This little gland, which is attached to your hypothalamus, makes hormones that control several other glands, such as your thyroid gland, adrenal glands, ovaries and testicles.
• Thyroid: Your thyroid is a butterfly-shaped gland in the front of your neck. It’s partially responsible for your metabolism (how your body uses energy from the food you eat).
• Parathyroid glands: These four tiny glands, which are usually located next to your thyroid gland, control the level of calcium and phosphorus in your body.
• Adrenal glands: You have two adrenal glands, one on top of each kidney. They control your metabolism, blood pressure, sexual development and response to stress.
• Pineal gland: This gland manages your sleep cycle by releasing melatonin.
• Pancreas: Your pancreas produces insulin, which is crucial to metabolism and controlling blood sugar levels. It’s also part of your digestive system.
• Ovaries: The ovaries release sex hormones called estrogen, progesterone and testosterone.
• Testes: The testes (testicles) make sperm and release the hormone testosterone.

What parts of the endocrine system are affected by multiple endocrine neoplasia type 1?

People with MEN type 1 develop tumors in multiple glands of their endocrine system. The most common affected areas include:

• Parathyroid glands (most common).
• Gastroenteropancreatic tract (a tumor can form in your pancreas or in other parts of the gastrointestinal tract, including your stomach and duodenum).
• Pituitary gland.

Most tumors associated with MEN type 1 are benign (noncancerous), but some tumors can be cancerous (malignant) and can spread to other areas of your body (metastasize).

Endocrine glands that are affected by tumors usually release excessive amounts of hormones into your bloodstream, which can result in a variety of symptoms and health issues.

Since MEN type 1 was discovered, healthcare providers have identified more than 20 different endocrine and non-endocrine tumors in individuals with MEN type 1. Other less common types of tumors that can form due to MEN type 1 include:

• Neuroendocrine tumors of your thymus (a lymphoid organ in your chest) and bronchi (the air passages in your lungs).
• Adrenocortical tumors (form in the outer layer of your adrenal glands).
• Lipomas (fatty tumors located just below your skin).
• Visceral leiomyomas (smooth muscle tumors).
• Truncal and facial collagenomas (excess collagen in the trunk of your body and face).
• Facial angiofibromas (a group of lesions that form on your face).
• Breast cancer.
• Meningioma (a primary central nervous system tumor, meaning it begins in your brain or spinal cord).
• Ependymomas (a type of tumor that can form in your brain or spinal cord).

What parts of the endocrine system are affected by multiple endocrine neoplasia type 2?

All people with MEN type 2 will develop medullary thyroid cancer (carcinoma), known as MTC. Medullary thyroid cancer represents approximately 1% to 2% of thyroid cancers in the United States. MTC is different from other types of thyroid cancers because it originates from a certain type of cell called C cells of the thyroid gland. These cells do not make thyroid hormone, like other cells in your thyroid do. C cells make a hormone called calcitonin, which lowers blood calcium levels.

MTC can spread (metastasize) to lymph nodes and other organs. The primary treatment for MTC is surgery in which a surgeon removes your thyroid (thyroidectomy).

People with MEN type 2 also develop one or both of the following two conditions:

• Pheochromocytoma: This is a rare tumor that forms in the middle of one or both of your adrenal glands (adrenal medulla). The tumor is made of a certain type of cell called chromaffin cells, which produce and release certain hormones. Most pheochromocytomas are benign (not cancer). Approximately 10% to 15% of pheochromocytomas may be malignant (cancer) and metastasize.
• Hyperparathyroidism (overactive parathyroid gland): Hyperparathyroidism happens when your parathyroid gland(s) release too much parathyroid hormone (PTH), which causes calcium levels in your blood to rise. This is usually caused by a benign parathyroid tumor (adenoma) or when two or more of your parathyroid glands become enlarged, a condition called hyperplasia.

Who does multiple endocrine neoplasia (MEN) affect?

Multiple endocrine neoplasia (MEN) affects males and females equally.

The onset of MEN type 1 can vary widely. It has been diagnosed in children as young as 8 and in adults as old as 80.

How common is multiple endocrine neoplasia (MEN)?

Multiple endocrine neoplasia (MEN) is a rare condition. MEN type 1 affects approximately 1 in 30,000 individuals, and MEN type 2 affects approximately 1 in 35,000 people.

Some researchers think that many cases of each type go undiagnosed or misdiagnosed, so the rate of the conditions could be higher.