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Multiple Endocrine Neoplasia: MEN Types 1 and 2

Multiple endocrine neoplasia (MEN) is a group of disorders that affect the endocrine system, which is made up of glands that produce, store, and release hormones into the bloodstream. The disease typically involves tumors (overgrowth of tissue) in multiple endocrine glands that may be cancerous or noncancerous (benign) and may cause the glands to become overactive and overproduce hormones. There are many forms of MEN, with the most common being type 1 and type 2.

  • Multiple endocrine neoplasia type 1 and type 2 are rare, with each subtype affecting up to one in 30,000-35,000 people.
  • Risk for MEN is similar in men and women and does not differ among people of different geographic or racial/ethnic groups.   

Multiple endocrine neoplasia runs in families meaning that the disease is passed down to family members through defects or mutations in certain genes, most commonly in MEN1 and RET (ret proto-oncogene). Only one parent needs to have the genetic defect to pass it on to a child.

Multiple Endocrine Neoplasia Type 1
This disorder most commonly involves tumors of pancreas, parathyroid glands, or pituitary gland. Most often, the tumors first appear in the parathyroid glands and the first sign of the disease is symptoms of overactive parathyroid glands (hyperparathyroidism), which means that the glands release too much calcium into the bloodstream. A person may have hyperparathyroidism for many years with no symptoms or have symptoms such as kidney stones, bone thinning, nausea and vomiting, high blood pressure (hypertension), weakness, and fatigue.

Most people who have the genetic trait for MEN1 will develop hyperparathyroidism by the age of 50.

Multiple Endocrine Neoplasia Type 2
Multiple endocrine neoplasia type 2 is divided into three subtypes: type 2A (approximately 90% of all cases), type 2B, and familial medullary thyroid carcinoma (FMTC). Most people with MEN2 develop medullary thyroid carcinoma regardless of their subtype. Some people with this disorder also may develop a tumor in their adrenal gland known as pheochromocytoma that may cause extremely high blood pressure. People with MEN2A also may develop hyperparathyroidism, which causes high calcium levels and people with MEN2B may develop tumors in nerve cells (ganglioneuromas) of the gastrointestinal tract and tumors in their lips, tongue, and eyelids (mucosal neuromas), often before the age of 10 years.

How is Multiple Endocrine Neoplasia Diagnosed?
Typically, this condition is diagnosed when a person has tumors in two or more endocrine glands; when a person has a tumor in one or more endocrine gland plus parent or sibling with a history of multiple endocrine neoplasia; or by genetic testing for specific mutations in genes associated with MEN even if the person does show signs or symptoms of the disease.

The disease is often detected by a blood test that shows higher than normal levels of hormones secreted by these glands or by genetic testing. People whose blood tests show abnormal hormone levels may need to undergo a CT scan or MRI to look for tumors.

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Multiple Endocrine Neoplasia: Genetic Testing and Treatment