COHORT SIZE RATHER THAN FOLLICLE-STIMULATING-HORMONE THRESHOLD LEVEL DETERMINES OVARIAN SENSITIVITY IN POLYCYSTIC-OVARY-SYNDROME

The aim of the presented study was to compare FSH threshold levels and ovarian response to stimulation with one of two standard increments o f exogenous FSH above the threshold in patients with polycystic ovary syndrome (PCOS) (n = 12) and eumenorrheic women (n = 11). The individu al FSH threshold was determined by treatment according to a low-dose, step-up protocol with urinary FSH (Metrodin; Ares Serono, Geneva, Swit zerland). In a subsequent treatment cycle, six PCOS patients and six e umenorrheic women were randomly assigned to double-blind treatment wit h the threshold dose plus Yz ampoule; the other six PCOS patients and five eumenorrheic women were treated with 1 ampoule above the threshol d dose. Determination of threshold levels showed no significant differ ences in median and range between PCOS patients and eumenorrheic women . The number of follicles on the day of human chorionic gonadotropin a dministration showed no significant correlation with the increase in F SH level above the threshold level. Irrespective of the dose given, th e number of follicles in the PCOS group was significantly higher than in eumenorrheic women. The higher sensitivity for gonadotropin stimula tion in patients with PCOS compared with women with regular menstrual cycles therefore appears not to be dependent on differences in FSH thr eshold level, but rather on the larger size of the FSH sensitive cohor t of small antral follicles.