Studies of the ZES patients have provided insights into the long-term effects of hypergastrinemia on the gastric mucosa and the possible risks of gastrin-enhanced growth effects particularly on stimulating the development of gastric neuroendocrine tumors, as well as other tumors and also on the nutritional effects of chronic hypo-/achlorhydria, rebound acid hypersecretion, and the occurrence of a number of other proposed PPI-related side-effects. Here, GAST is linked to gastric neuroendocrine tumor, well differentiated, low or intermediate grade.