Relaxins are known endocrine and autocrine/paracrine hormones, belonging to the insulin gene superfamily. In the human there are three non-allelic relaxin genes, RLN1, RLN2 and RLN3. RLN1 and RLN2 share high sequence homology. The active form of the encoded protein consists of an A chain and a B chain but their cleavage sites are not definitely described yet. 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. There are two alternatively spliced transcript variants encoding different isoforms described for this gene.