Exendin-4 (3-39) is a peptide. Exendin-4 (3-39) is a truncated form of Exendin-4 (HY-13443) that lacks the first two amino acids. Exendin-4 is a potent Glucagon-like peptide-1 receptor (GLP-1r) agonist. Exendin-4 (3-39) and Exendin-4 can be used for the research of diabetic and hypothalamic-pituitary-adrenal (HPA) axis.