Lactational amenorrhoea is due to

Ans. is 'a' i.e. Prolactin induced inhibition of GnRH Suppression of the female ovarian cycles in nursing mothers for many months after delivery.In most nursing mothers, the ovarian cycle and ovulation does not resume until a few weeks after cessation of nursing the babyThe cause of this seems to be that the same nervous signals from the breasts to the hypothalamus that cause prolactin secretion during suckling either because of the nervous signals themselves or because of the subsequent effect of the increased prolactin, inhibit secretion of gonadotropin releasing hormone by the hypothalamus.This in turn, suppresses the formation of the pituitary gonadotrophic hormones, leutinizing hormones and follicle stimulating hormone.Yet, after several months of lactation in some mothers, especially in those who nurse their babies only part of the time, the pituitary does begin again to secrete sufficient gonadotropic hormones to reinstate the monthly sexual cycle even though nursing continues.