The rise of estradiol and inhibin B after acute stimulation with follicle-stimulating hormone predict the follicle cohort size in women with polycystic ovary syndrome, regularly menstruating women with polycystic ovaries, and regularly menstruating women with normal ovaries.

Polycystic ovaries contain a larger number of antral follicles than control ovaries. The aim of this study was to test whether the increase in estradiol (E(2)) and inhibin B after stimulation with 300 IU recombinant FSH in the early follicular phase and the ovarian volume can predict the size of the follicle cohort in polycystic ovary syndrome (PCOS) patients (n = 10), patients with polycystic ovaries detected by ultrasound but with regular menstrual cycles (PCO; n = 10), and regularly menstruating patients with normal ovaries (n = 10). The follicle cohort size was measured as the FSH-sensitive follicles growing during a standardized in vitro fertilization stimulation. Linear regression analysis showed that the slopes of the regression lines of the E(2) increment and the inhibin B increment in relation to the number of follicles were not significantly different among the three groups, meaning that an increased sensitivity for FSH of the granulosa cells of polycystic ovaries was not found. For the total group (n = 30) we calculated that an E(2) increment of 100 pmol/L predicts 5.5 follicles (95% confidence interval, 2.8--8.2; r = 0.617; P < 0.001), and an inhibin B increment of 100 ng/L predicts 6.2 follicles (95% confidence interval, 3.5--9.0; r = 0.665; P < 0.001). The ovarian volume could not be used in a prediction model because the association with the number of follicles was different in the PCO group compared with the PCOS and the control group. Women with PCO and women with PCOS both had a follicle cohort twice as big as the cohort in control women (P < 0.01). The differences in menstrual cycle pattern between the PCO and PCOS groups cannot be explained by differences in cohort size.