[1] Individuals suffering from this disorder are prone to developing multiple endocrine and nonendocrine tumors.

[5] About 10-15% of islet cell tumors originate from a β-cell, secrete insulin (insulinoma), and can cause fasting hypoglycemia.

A severe secretory diarrhea can develop and cause fluid and electrolyte depletion with non–β-cell tumors.

Carcinoid tumors, particularly those derived from the embryologic foregut (lungs, thymus), occur in isolated cases.

People with multiple endocrine neoplasia type 1 are born with one mutated copy of the MEN1 gene in each cell.

This is known as Knudson's two-hit hypothesis[7] and is a common feature seen with inherited defects in tumor suppressor genes.

Oncogenes can become neoplastic with only one activating mutation, but tumor suppressors inherited from both mother and father must be damaged before they lose their effectiveness.

[8] The exact function of MEN1 and the protein, menin, produced by this gene is not known,[9] but following the inheritance rules of the "two-hit hypothesis" indicates that it acts as a tumor suppressor.

Hormones are chemical messengers that travel through the bloodstream and regulate the function of cells and tissues throughout the body.

These disorders greatly increase the risk of developing multiple cancerous and noncancerous tumors in glands such as the parathyroid, pituitary, and pancreas.

MEN1-associated overactivity of these three endocrine organs are briefly described here: The treatment of choice of parathyroid tumors is open bilateral exploration with subtotal (3/4) or total parathyroidectomy.

The treatment discovered by Joseph Shepherd in 1997-2001 does not provide a cure, rather extends life expectancy.

[3] Endocrine pancreatic tumor are treated with surgery and cytotoxic drugs in case of malignant disease.