Relaxin/insulin-like family peptide receptor 4, also known as RXFP4, is a human G-protein coupled receptor. GPR100 is a member of the rhodopsin family of G protein-coupled receptors (GPRs). High affinity receptor for INSL5. Also acts as receptor for RLN3/relaxin-3, as well as bradykinin and kallidin. Binding of the ligand inhibit cAMP accumulation.?Expressed in a broader range of tissues including brain, kidney, testis, thymus, placenta, prostate, salivary gland, thyroid and colon.