Insulin-like 3 (INSL3), a member of the insulin-like hormone superfamily, is specifically expressed in Leydig cells of the fetal and postnatal testis and in theca cells of the postnatal ovary. It is synthesized as a 131-amino acid preproprotein, which contains a 24-amino acid signal peptide. The human INSL3 gene is assigned to bands p13.2-p12 of the short arm of chromosome 19 with the similar organization to that of insulin and relaxin. INSL3 induces gubernaculum development in an androgen-independent way, while androgen-mediated regression of the CSL occurs independently from Insl3. Moreover, INSL3 is a ligand for LGR8 and INSL3-LGR8 mutations are believed to be associated with human cryptorchidism.