Comparison of the efficacy of the aromatase inhibitor letrozole and clomiphen citrate gonadotropins in controlled ovarian hyperstimulation: a prospective, simply randomized, clinical trial.

ObjectiveTo study the efficacy of the aromatase inhibitor letrozole in controlled ovarian hyperstimulation (COH).Material and methodsIn this prospective simply randomized clinical trial, one hundred forty patients with unexplained infertility undergoing intrauterine insemination (IUI) therapy were randomized to receive either letrozole or clomiphene citrate (CC)-gonadotropin. The patients were selected among patients referred to one university hospital and one private infertility clinic. A letrozole dose of 5 mg/day (n = 70) was given on days 3-7 of the menstrual cycles. Clomiphen citrate a dose of 100 mg/day was given like letrozole but combined with human menopausal gonadotropin (hMG) dose of 75 IU/ml administered every day starting on day 6. Ovulation was triggered with urinary hCG (10,000 IU) when the leading follicle(s) reached 18 mm in diameter. A single IUI was performed 36 hours later. The luteal phase was supplemented with micronized progesterone vaginally. Ovarian stimulation response (E2 levels and number of follicles) was primary outcome.ResultsThere were no differences in demographic characteristics between groups. The number of mature follicles (1.8 +/- 0.7 vs. 2.46 +/- 2.3; P = 0.042) and serum E2 level on the day of hCG (310 +/- 135.4 vs. 1,670.7 +/- 1021.8 pg/ml, respectively; P < 0.0001) were significantly lower in letrozole group. A significantly higher endometrial thickness was observed at the time of hCG administration in patients that received letrozole (9.7 +/- 1.6 mm vs. 7.8 +/- 2 mm; P < 0.001). Clinical pregnancy rates also were significantly higher in letrozole group (32.8% vs. 14.3%, respectively; P < 0.01).ConclusionThe aromatase inhibitor letrozole appears to constitute a good alternative to CC-gonadotropin in patients with unexplained infertility undergoing COH cycles combined with IUI therapy.