Question 220

Question:

Serum samples from a healthy woman with a history of regular 28-day menstrual cycles show a peak in the serum concentration of 17beta-estradiol over the past 12 hours. No progesterone is detectable. Within 3 days, which of the following is expected to occur?

Correct Answer: D.  Ovulation

17 beta-estradiol is the major form of estrogen present in a woman’s body from menarche to menopause. Its role in menstruation is primarily during the proliferative phase (day 1-14) to increase the size of the endometrium and prepare it for the progesterone-dominated secretory phase (day 15-28) during which an embryo will potentially implant and spiral vessels will penetrate the layers of the endometrium. Estradiol peaks on day 13, and a surge of positive feedback on luteinizing hormone (LH) by estradiol during this period causes the follicle to burst on day 14 of the cycle, releasing the egg. Progestone levels are at their lowest during this period, and it is only the secretion of progesterone by the remnants of the follicle, the corpus luteum, that causes a rise in progesterone levels in the second phase of the cycle.