These disorders greatly increase the risk of developing multiple cancerous and noncancerous tumors in glands such as the parathyroid, pituitary, and pancreas. Multiple endocrine neoplasia occurs when tumors are found in at least two endocrine glands. Tumors can also develop in organs and tissues other than endocrine glands. If the tumors become cancerous, some cases can be life-threatening. The disorder affects 1 in 30,000 people.
Although many different types of hormone-producing tumors are associated with multiple endocrine neoplasia, tumors of the parathyroid gland, pituitary gland, and pancreas are most frequent in multiple endocrine neoplasia type 1. Tumors cause an overactivation of these hormone-producing glands, leading to serious health problems such as severe ulcers. Overactivity of the parathyroid gland (hyperparathyroidism) is the most common sign of this disorder. Hyperparathyroidism disrupts the normal balance of calcium in the blood, which can lead to kidney stones, thinning of bones, weakness, and fatigue.
Neoplasia in the pituitary gland can manifest as prolactinomas whereby too much prolactin is secreted, suppressing the release of gonadotropins, causing a decrease in sex hormones such as testosterone.
The two major types of multiple endocrine neoplasia, type 1 and type 2, are often confused because they have similar names. These types are distinguished by the genes involved, the hormones that are affected, and their characteristic signs and symptoms. They are also very different in their options for cancer.
Mutations in the MEN1 gene cause multiple endocrine neoplasia type 1. The function of the MEN1 gene is unknown.The MEN1 gene is located in Chromosome 11q13 and the gene product is Menin (a cofactor for transcription). Researchers believe that it acts as a tumor suppressor, which means it normally keeps cells from growing and dividing too rapidly or in an uncontrolled way. If mutations inactivate both copies of the MEN1 gene, cells can grow and divide in a poorly controlled way to form tumors.
Most cases of multiple endocrine neoplasia type 1 are inherited in an autosomal dominant pattern, which means affected people may have affected siblings and relatives in successive generations (such as parents and children). An affected person usually has one parent with the condition. Some cases, however, result from new mutations in the MEN1 gene. These cases occur in people with no history of the disorder in their family.