Peptide receptors constitute a large group of GPCRs that are activated by extracellular protein or peptide ligands. Endogenous peptide receptor ligands bind to the N' terminus and/or the 3 extracellular loops of the receptor. Consistent with the array of physiological roles of peptide receptors, the range of conditions in which they are dysregulated is vast and includes cardiovascular, endocrine and metabolic disorders.