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Physiology · Reproduction: lactational amenorrhoea
Sample itemA woman exclusively breastfeeding her 4-month-old infant remains amenorrhoeic and anovulatory. Which mechanism chiefly explains this lactational amenorrhoea?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
C. Suckling suppresses pulsatile GnRH release, reducing LH pulses and follicular maturation
Suckling and the associated hyperprolactinaemia suppress hypothalamic GnRH pulse generation, so LH pulses are too infrequent to support follicular growth and ovulation. This is the physiological basis of the lactational amenorrhoea method of contraception when breastfeeding is exclusive. Fertility returns as suckling frequency falls.
Option by option
A. Oxytocin blocks oestrogen receptors in the ovary
Oxytocin has no ovarian oestrogen-receptor blocking action.
B. Prolactin directly destroys the corpus luteum
Prolactin acts by inhibiting GnRH release, not by destroying luteal tissue.
C. Suckling suppresses pulsatile GnRH release, reducing LH pulses and follicular maturation (correct)
Correct. Reduced GnRH pulsatility prevents ovulation during intense suckling.
D. Raised FSH from the pituitary arrests follicles
FSH is not elevated; gonadotrophin pulsatility is suppressed.
Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.
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