Glucagon-like Peptide-1 is synthesized in intestinal L-cells in response to the presence of glucose and fatty acids absorbed from the intestine. Most GLP-1 is the GLP-1 (7-36) amidated form; some GLP-1 is the GLP-1 (7-37) form. GLP-1 circulates to the pancreas where it binds the Glucagon-like Peptide-1 Receptor (GLP-1R), a G-protein coupled receptor located on the plasma membrane of beta cells. GLP-1R is a seven-pass transmembrane protein and a member of the B family of GPCRs, which have N-terminal extracellular domains of 100-150 amino acids. GLP-1 interacts with the extracellular N-terminal region of GLP-1R.