ZES is caused by tumors called gastrinomas, which release the hormone gastrin.
Normally, cells in the stomach produce and control gastrin so only the right amount is released. Gastrin travels through the bloodstream to signal other cells in the stomach to release gastric acid to help break down food. Gastrinomas release abnormal amounts of gastrin, resulting in excess gastric acid in the stomach and duodenum. The excess acid eventually causes sores called peptic ulcers to form in the lining of the duodenum.
Scientists are unsure what causes the majority of gastrinomas, which appear sporadically. About 25 percent of gastrinoma cases are caused by an inherited genetic disorder called multiple endocrine neoplasia type 1 (MEN1). MEN1 can cause a variety of hormone-releasing tumors such as prolactinomas and insulinomas. Prolactinomas form in the pituitary gland in the brain and cause excess prolactin—a hormone that influences milk production, fertility, and bone strength. Insulinomas form in the pancreas and cause excess insulin—a hormone that helps control blood glucose, also called blood sugar. Signs and symptoms of MEN1 include increased hormone levels in the blood, kidney stones, diabetes, muscle weakness, and weakened bones and fractures.