The principal hormones secreted by the testes is known as androgen. Androgen is of two types namely testosterone and androstenedione. In mammals, testosterone is responsible for the production of primary and secondary sex characters and helps in the development of seminiferous tubules. From ovary, various hormones are secreted namely estrogen, progesterone, and relaxin. Estrogen helps in secondary sex character development; whereas, progesterone facilitates the development of secondary sex characteristics, and maintain pregnancy and gestation period. Relaxin relaxes pubic ligaments and favors parturition.