Relaxin
Polypeptide hormone (structure similarity to inzulin)
produced by corpus luteum, uterus, placenta, mammary glands in women and by prostate gland in men
during pregnancy softens and dilates uterine cervix (facilitates delivery)
non-pregnant women - corpus luteum and endometrium in secretory phase - function unknown
men - in sperm - maintain sperm motility and ovum penetration