Ans. is d, i.e. Defect in pituitary gonadal axisRef: Dutta Gynae 6th/ed, p467; Leon Speroff 7th/ed, p404-409Withdrawal bleeding following administration of progesterone suggests:* The uterus is sufficiently primed with estrogen, i.e. production of endogenous estrogen is normal which means. Ovaries and hypothalamic pituitary axis are functioning normally.* The outflow tract (uterus) is normal and endometrium is responsive to estrogen.* There is a defect in production of progesterone (so pregnancy ruled out).