Glucagon-like peptide-1 (GLP-1) is a neuropeptide and an incretin derived from the transcription product of the proglucagon gene. The major source of GLP-1 in the periphery is the intestinal L cell that secretes GLP-1 as a gut hormone; the major source in the brain is the nucleus of the solitary tract, which is the source of a widely distributed set of GLP-1 projection neurons. The biologically active forms of GLP-1 are: GLP-1-(7-37) and GLP-1-(7-36)NH2. Those peptides result from selective cleavage of the proglucagon molecule.

Once in the circulation, GLP-1 has a half-life of less than 2 minutes, due to rapid degradation by the enzyme dipeptidyl peptidase-4. It is a potent antihyperglycemic hormone, inducing glucose-dependent stimulation of insulin secretion while suppressing glucagon secretion.