CRHR1, also known as CHR-R1 and Corticotropin Releasing Factor Receptor 1, CRF 1, is a member of the Class B G protein-coupled receptor family that mediates the action of hypothalamic and peripheral CRH. It is the key regulator of the stress response in the hypothalamic-pituitary adrenal axis and an important functional mediator of the endocrine, cardiovascular, gastrointestinal, and immune systems. The other major endogenous ligand for CRHR1 is Urocortin 1.