RLN2, as known as prorelaxin H2 isoform 1, belongs to the insulin gene superfamily. This family 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. It is 18kD in size and 185aa in length. It contains a 24aa signal sequence, a 3.3kD, 29aa B domain, a 106aa C (or connecting) domain, and a C-terminal, 2.7kD, 24aa A domain.