A 28-year-old woman is exclusively breastfeeding her 3-month-old infant and has not resumed menstruation. Serum prolactin is elevated. Through which primary mechanism does prolactin suppress ovulation during lactation?

• A Direct inhibition of ovarian granulosa cell aromatase activity
• B Stimulation of ovarian inhibin B secretion
• C Downregulation of pituitary LH receptors
• D Suppression of hypothalamic GnRH pulsatile secretion ✓

Explanation

Elevated prolactin during lactation suppresses hypothalamic GnRH pulsatility, leading to reduced FSH and LH secretion (lactational amenorrhea). This is mediated via increased hypothalamic dopamine and modulation of kisspeptin neurons. Option A is incorrect because prolactin does not directly inhibit ovarian aromatase. This mechanism explains the contraceptive effect of exclusive breastfeeding.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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