Zollinger-Ellison syndrome is a rare condition in which a tumor called a gastrinoma forms in the pancreas or small intestine. The tumor releases a hormone called gastrin that causes production of excess stomach acid.

Almost all people who have Zollinger-Ellison syndrome get an ulcer at some point, usually in the small intestine (duodenal ulcer). Ulcers produced by this disease are more difficult to cure than ulcers from other causes.

In more than half of the people with Zollinger-Ellison syndrome, the tumors (gastrinomas) are cancerous and can spread to the lymph nodes and liver.

The main treatment for Zollinger-Ellison syndrome is removal of the tumors and taking acid-reducing medicines called proton pump inhibitors.