Effectiveness of Letrozole for Iinduction of Ovulation in Polycystic Ovarian Syndrome(PCOS) Patients with an Inadequate Response to Clomiphene Ditrate

Objective To evaluate the effectiveness of letrozole for induction of ovulation in PCOS patients with an inadequate response to clomiphene citrate(CC).Methods Twenty-one patients with anovulatory polycystic ovarian syndrome(PCOS) were included in this study,who had previously received CC with an inadequate outcome(no ovulation and/ or endometrial thickness of ≤0.5 cm).The follicle diameter,endometrial thickness,the level of estradiol(E2) and the score of cervical mucus were monitored while the day of HCG injection.Results With letrozole treatment,ovulation occurred in 14/21(66.7%) of cycles versus 12/37(32.4%) of cycles with CC(P 0.01).The mean endometrial thickness was 7.3 mm with letrozole versus 5.8 mm with CC(P 0.01).The E2 level of group letrozole were significantly lower than that of group CC,and the cervical mucus score of group letrozole were significantly higher than that of group CC.Pregnancy were achieved in 3 letrozole patients(14.3%).Conclusion Oral administration of the aromatase inhibitor letrozole is effective for ovulation induction in PCOS with a poor response to CC.Letrozole appears to avoid the unfavorable effects frequently seen with antiestrogen used for ovulation induction.