PANCREAS AND MEN1

THE PANCREAS AND DUODENUM

Located behind the stomach, the pancreas has two major roles: to release digestive juices into the intestines and key hormones into the bloodstream. The duodenum is the first part of the small intestine next to the pancreas.

The pancreatic hormones are normally produced by small clusters of specialized cells called pancreatic islets. Some of the major hormones produced by the pancreatic islets are:

• Insulin – lowers blood glucose, also called blood sugar
• Glucagon – raises blood glucose
• Somatostatin – inhibits secretion of certain other hormones
• Vasoactive Intestinal Peptide (VIP) – causes intestinal cells to secrete water into the intestine
• Gastrin – causes the stomach to produce acid for digestion

GASTRINOMAS

In MEN1, gastrin may be oversecreted by tumors called gastrinomas in the pancreas, duodenum, and lymph glands. If exposed to too much gastrin, the stomach releases excess acid, leading to the formation of severe ulcers in the stomach and small intestine. In addition, too much gastrin usually causes serious diarrhea.

People with MEN1 have about a 20 to 60 percent chance of developing gastrinomas. The illness associated with these tumors is called Zollinger-Ellison syndrome. The ulcers caused by untreated gastrinomas are much more dangerous than typical stomach or intestinal ulcers. Left untreated, they can cause rupture of the stomach or intestine and even death.

The gastrinomas associated with MEN1 are not easily cured through tumor surgery because finding the many small gastrinomas in the pancreas, duodenum, and lymph glands is difficult. The mainstay of treatment is powerful medicines called acid pump inhibitors that block stomach acid release. Taken by mouth, these medicines have proven effective in controlling the complications of excess gastrin in most cases of Zollinger-Ellison syndrome.

RARE PANCREATIC COMPLICATIONS

Occasionally, a person who has MEN1 develops an islet tumor of the pancreas that secretes high levels of hormones. Insulinomas, for example, produce too much insulin, causing hypoglycemia, or low blood glucose. About 10 percent of adults with MEN1 develop insulinomas. Rare pancreatic tumors may secrete too much glucagon, which can cause diabetes, or too much VIP, which can cause watery diarrhea.

Tumors that secrete adrenocorticotropin (ACTH) may also arise in the pancreas. ACTH is normally secreted by the pituitary gland and stimulates the adrenal glands to produce cortisol, a hormone that helps the body respond to stress. Tumors in the pancreas may also infrequently secrete gonadotropin-releasing hormone (GnRH). GnRH is normally secreted by the hypothalamus and stimulates the pituitary gland to release follicle stimulating hormone (FSH), which regulates fertility in men through sperm production and in women through ovulation. In general, surgery is the mainstay of treatment for these uncommon types of tumors.

Source: National Endocrine and Metabolic Diseases Information Service (NEMDIS), a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK); National Institutes of Health (NIH)