Zollinger-Ellison Syndrome

Zollinger-Ellison syndrome (ZES) is the clinical syndrome produced by a gastrinoma, a gastrin-secreting neuroendocrine tumour (NET). Gastrin normally stimulates the parietal cells of the stomach to secrete hydrochloric acid, and its release is switched off once the stomach becomes acidic. A gastrinoma releases gastrin continuously and ignores that feedback, so the stomach secretes large volumes of acid around the clock. This combination of hypergastrinemia and acid hypersecretion explains almost every feature of the disease. Most gastrinomas arise in the duodenum or pancreas. A 2021 review in the World Journal of Gastroenterology reports a duodenal location in 60% to 90% of patients and a pancreatic location in about 25%; duodenal tumours are often small and can be multiple, which makes them hard to find. ZES is rare: the US National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) reports that 0.5 to 3 people per million are diagnosed each year, slightly more often men than women. Most cases are sporadic. The remainder occur with multiple endocrine neoplasia type 1 (MEN1), an autosomal dominant tumour syndrome. Sources give slightly different proportions:...