Aging women with polycystic ovary syndrome who achieve regular menstrual cycles have a smaller follicle cohort than those who continue to have irregular cycles

Objective: To examine whether follicle loss due to ovarian aging is responsible for the occurrence of regular menstrual cycles in aging women with polycystic ovary syndrome (PCOS), the size of the FSH-sensitive follicle cohort was estimated by the exogenous follicle-stimulating hormone ovarian reserve test (EFORT) and related to the follicle count as measured by ultrasound. Design: Prospective study. Setting: Reproductive endocrinology unit of an academic medical center. Patient(s): Twenty-seven aging women with PCOS (35.8-49.4 years): 20 with regular menstrual cycles and 7 with oligomenorrhea or amenorrhea. Intervention(s): EFORT and transvaginal ultrasound. Main Outcome Measure(s): Baseline (cycle day 2, 3, or 4) FSH, androstenedione (A), T, E₂, and inhibin B levels, the E₂ and inhibin B increment after the EFORT, and the follicle count. Result(s): After correction for the body mass index (BMI), the inhibin B increment was higher in the irregular menstrual group, but the E₂ increment did not differ significantly between the two groups. Ultrasound showed a median follicle count of 8.5 (4.0-18.0) in women with regular menstrual cycles (n = 16), compared with 18.0 (8.0-35.0) in irregularly menstruating women (n = 7). The follicle count was significantly correlated to the FSH-induced E₂ increment (r = 0.656) as well as to the inhibin B increment (r = 0.654). The regularly menstruating group was significantly older, had a higher basal FSH concentration, and had lower androgens than the irregularly menstruating group. Conclusion(s): The smaller follicle count, the older age, the higher FSH concentration, and the lower FSH-induced inhibin B increment found in women with PCOS and a regular menstrual cycle confirm that a decrease in the size of the follicle cohort due to ovarian aging is largely responsible for the regular menstrual cycles in aging PCOS women.