Gastrin, nke a makwaara dị ka pepsin, bụ hormone nke eriri afọ nke na-ezobe ya site na mkpụrụ ndụ G nke antrum na duodenum ma na-arụ ọrụ dị mkpa n'ịhazi ọrụ tract digestive na ịnọgide na-enwe nhazi nke tract digestive. Gastrin nwere ike kwalite secretion nke gastric acid, mee ka mkpụrụ ndụ mucosal nke eriri afọ na-eto eto, na-eme ka nri na-edozi ahụ na ntinye ọbara nke mucosa. N'ime ahụ mmadụ, ihe karịrị 95% nke gastrin na-arụ ọrụ ndụ bụ α-amidated gastrin, nke kachasị nwere isomers abụọ: G-17 na G-34. G-17 na-egosi ọdịnaya kachasị elu na ahụ mmadụ (ihe dịka 80% ~ 90%). A na-achịkwa nzuzo nke G-17 site na uru pH nke antrum gastric ma gosipụta usoro nzaghachi na-adịghị mma nke metụtara gastric acid.