Signs and symptoms of Zollinger-Ellison syndrome may include:

• Abdominal pain
• Diarrhea
• Burning, aching, gnawing or discomfort in your upper abdomen
• Acid reflux and heartburn
• Nausea and vomiting
• Bleeding in your digestive tract
• Unintended weight loss
• Decreased appetite

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.

If you have a blood relative, such as a sibling or parent, with MEN 1, it's more likely that you'll have Zollinger-Ellison syndrome.