Zollinger-Ellison syndrome is caused by tumors called gastrinomas. These growths are most often found in the head of the pancreas and the upper small intestine. High levels of gastrin cause production of too much stomach acid.

Gastrinomas may occur as single tumors or several tumors. One half to two thirds of single gastrinomas are cancerous (malignant) tumors. These tumors often spread to the liver and nearby lymph nodes.

Many people with gastrinomas have several tumors as part of a condition called multiple endocrine neoplasia type I (MEN I). Tumors may develop in the pituitary gland (brain) and parathyroid gland (neck) as well as in the pancreas.

Symptoms may include:

• Abdominal pain
• Diarrhea
• Vomiting blood (sometimes)
• Severe esophageal reflux (GERD) symptoms

Signs include ulcers in the stomach and small intestine.

Tests include:

• Abdominal CT scan
• Calcium infusion test
• Endoscopic ultrasound
• Exploratory surgery
• Gastrin blood level
• Octreotide scan
• Secretin stimulation test

Medicines called proton pump inhibitors (omeprazole, lansoprazole, and others) are used for treating this problem. These medicines reduce acid production by the stomach. This helps the ulcers in the stomach and small intestine heal. These medicines also relieve abdominal pain and diarrhea.

Surgery to remove a single gastrinoma may be done if the tumors have not spread to other organs. Surgery on the stomach (gastrectomy) to control acid production is rarely needed.

The cure rate is low, even when it is found early and the tumor is removed. However, gastrinomas grow slowly. People with this condition may live for many years after the tumor is found. Acid-suppressing medicines work well to control the symptoms.

Complications may include:

• Failure to locate the tumor during surgery
• Intestinal bleeding or hole (perforation) from ulcers in the stomach or duodenum
• Severe diarrhea and weight loss
• Spread of the tumor to other organs

Contact your health care provider if you have severe abdominal pain that does not go away, especially if it occurs with diarrhea.

Z-E syndrome; Gastrinoma; ZES

De Herder WW, Feelders RA, Hofland J. Neuroendocrine tumors and disorders. In: Melmed S, Auchus RJ, Goldfine AB, Rosen CJ, Kopp PA, eds. Williams Textbook of Endocrinology. 15th ed. Philadelphia, PA: Elsevier; 2025:chap 43.

Strosberg JR, Al-Toubah T. Neuroendocrine tumors. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 34.

Updated by: Jenifer K. Lehrer, MD, Gastroenterologist, Philadelphia, PA. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.