Gastrin is a peptide hormone that is a major physiological regulator of gastric acid section and a promoter of gastric mucosal growth. It binds to cholecystokinin B receptors (CCKBR) and stimulates an increase in intracellular CA++, the production of inositol phosphate, and the activation of protein kinase C. Gastrin is also involved in gastric epithelial cell proliferation and maturation and is utilized in gastrointestinal organoids research.