Glucagon-like Peptides GLP-1 is highly conserved across species, suggesting that it is physiologically important. It is secreted in a cleaved form, GLP-17–36NH2, which contains the thirty carboxy-terminal amino acids; this form inhibits secretion of gastric acid and is a more potent stimulus to insulin secretion than GIP. The physiological function of the thirty-five amino acid GLP-2 is unknown.