Lactational amenorrhea is due to:

In breastfeeding females, prolactin levels are increased in response to suckling stimulus of breast feeding. Besides prolactin, FSH concentration are normal and LH concentration are low. Despite the presence of gonadotropin the ovary during lactation hyperprolactinemia dose not display follicular development and dose not secrete estrogen These observations suggest that high concentrations of prolactin can work at both central levels(by inhibiting pulsatile secretion of GnrH) and peripheral level i.e. ovarian sites to produce lactational amenorrhea and anovulation The principle pf GnrH suppression by prolactin is reinforced by the demonstration that treatment of amenorrheic, lactating women with pulsatile GrrH , fully restores pituitary secretion and normal ovarian cyclic activity