The most complete data in one study come from a large NIH prospective study involving 57 consecutive patients with MEN1/ZES [61], in whom at the time of the gastric biopsies, the ZES had been present a mean of 11.4 years (range, 0.5–31.4 years), and the patients had all had chronic hypergastrinemia at the time of the biopsy with the FSG elevated a mean of 4.7-fold above normal (range—1–1100-fold increased). This evidence concerns the gene MEN1 and Zollinger-Ellison syndrome.