Home › MCQs › MBBS › Question #10295
Back to Questions
MBBS QUESTION #10295
Question 1
The mid-cycle luteinizing hormone (LH) surge, which triggers ovulation, is a striking example of positive feedback in endocrinology. This surge is triggered by:
  • Sustained negative feedback of estrogen on the hypothalamic-pituitary axis throughout the cycle
  • A sustained high level of estrogen from the maturing dominant follicle switching from negative to positive feedback on GnRH/LH secretion✔️
  • A sudden fall in progesterone levels
  • Direct stimulatory feedback from inhibin on the pituitary
Correct Answer Explanation
Throughout most of the follicular phase, rising estrogen exerts negative feedback on gonadotropin secretion; however, once estrogen reaches a high, sustained level from the dominant follicle, its feedback effect switches to positive, triggering the surge of GnRH and LH that precipitates ovulation — one of the few examples of physiological positive feedback.