Relaxins are known endocrine and autocrine/paracrine hormones, belonging to the insulin gene superfamily. In humans there are three non-allelic relaxin genes, RLN1, RLN2 and RLN3, where RLN1 and RLN2 share high sequence homology. The protein encoded by this gene is synthesized as a single-chain polypeptide but the active form consists of an A chain and a B chain linked by disulfide bonds. Relaxin is produced by the ovary, and targets the mammalian reproductive system to ripen the cervix, elongate the pubic symphysis and inhibit uterine contraction. It may have additional roles in enhancing sperm motility, regulating blood pressure, controlling heart rate and releasing oxytocin and vasopressin.