<prompt> Lactational amenorrhea is due to :Prolactin induced inhibition of GnRHProlactin induced inhibition of FSHOxytocin induced inhibition of GnRHAll  <response>: Ans. is a i.e. Prolactin induced inhibition of GnRH In breast feeding females, prolactin levels are increased in response to suckling stimulus of breast feeding. Besides iProlactin, FSH concentrations are normal and LH concentrations are low. Despite the presence of gonadotropin the ovary during lactational hyperprolactinemia does not display follicular development and does not secrete estrogen. These observations suggest that high concentrations of prolactin can work at both central level by inhibiting pulsatile secretion of GnRH and peripheral level i.e. ovarian sites by inhibiting synthesis of progesterone and by changing testosteronedihydrotestosterone ratio i.e. increasing local anti estrogen concentrations to produce lactational amenorrhea and anovulation. The principle of GnRH suppression by prolactin is reinforced by the demonstration that, treatment of amenorrheic, lactating women with pulsatile GnRH, fully restores pituitary secretion and normal ovarian cyclic activity. 