The exact cause of Zollinger-Ellison syndrome remains unknown. But the sequence of events that occurs in Zollinger-Ellison syndrome is clear. The syndrome begins when a tumor (gastrinoma) or tumors form in your pancreas, duodenum or the lymph nodes adjacent to your pancreas.
Your pancreas sits behind and below your stomach. It produces enzymes that are essential to digesting food. The pancreas also produces several hormones including insulin, a hormone that helps to control your blood glucose.
Digestive juices from the pancreas, liver and gallbladder mix in the duodenum, the part of the small intestine next to your stomach. This is where digestion reaches its peak.
The tumors that occur with Zollinger-Ellison syndrome are made up of cells that secrete large amounts of the hormone gastrin. Increased gastrin makes the stomach produce far too much acid. The excessive acid then leads to peptic ulcers and sometimes to diarrhea.
Besides causing excess acid production, the tumors are cancerous (malignant). Although the tumors tend to grow slowly, the cancer can spread elsewhere — most commonly to nearby lymph nodes or your liver.
Association with MEN 1
Zollinger-Ellison syndrome may be caused by an inherited condition called multiple endocrine neoplasia, type 1 (MEN 1). People with MEN 1 also have tumors in the parathyroid glands and may have tumors in their pituitary glands.
About 25 percent of people who have gastrinomas have them as part of MEN 1. They may also have tumors in the pancreas and other organs.