Serum anti-Mullerian hormone levels are negatively related to Follicular Output RaTe (FORT) in normo-cycling women undergoing controlled ovarian hyperstimulation

background: Since in rodents anti-Mullerian hormone (AMH) has been shown to inhibit antral follicle responsiveness to FSH, we aimed at verifying whether a relationship exists between serum AMH levels and antral follicle responsiveness to exogenous FSH in normo-cycling women. methods: Serum AMH, estradiol (E2) and FSH levels were prospectively measured on cycle day 3 in patients undergoing controlled ovarian hyperstimulation (COH) with a time-release GnRH agonist and standardized FSH doses. In 162 patients, follicles were counted after pituitary suppression and before FSH administration (baseline; small antral follicles; 3-8 mm), and on the day of hCG (dhCG; pre-ovu- latory follicles; 16 -22 mm). Antral follicle responsiveness to FSH was estimated by the Follicular Output RaTe (FORT), determined by the ratio pre-ovulatory follicle count on dhCG × 100/small antral follicle count at baseline. results: Serum AMH levels were positively correlated with the number of small antral follicles at baseline (r ¼ 0.59; P , 0.0001) and pre-ovulatory follicles on dhCG (r ¼ 0.17; P , 0.04). Overall, FORT was 47.5+ 1.4% and failed to be influenced by the woman's age, BMI or basal E2 and FSH level. Conversely, multiple regression analysis showed that FORT was negatively correlated with AMH levels (r ¼ 20.30; P , 0.001), irrespective of duration of COH and total FSH dose. conclusions: The percentage of follicles that effectively respond to FSH by reaching pre-ovulatory maturation is negatively and inde- pendently related to serum AMH levels. Although the mechanisms underlying this finding remain unclear, it is in keeping with the hypothesis that AMH inhibits follicle sensitivity to FSH.