Use of an aromatase inhibitor in patients with polycystic ovary syndrome: a prospective randomized trial

To compare the use of an aromatase inhibitor (letrozole) with the use of clomiphene citrate (CC). Prospective randomized study. An infertility clinic in a university hospital. Seventy-four consecutive infertile patients with polycystic ovary syndrome were recruited. Thirty-eight patients were randomized to the letrozole group (99 cycles), and the remaining patients were recruited to the CC group (95 cycles). The aromatase inhibitor letrozole (2.5 mg/d) and CC (100 mg/d) were administered orally on days 3–7 of menses. Number of follicles, endometrial thickness, E 2 levels on hCG day, and pregnancy rates among both groups. Ovulation occurred in 65.7% (65/99) of letrozole cycles and in 74.7% (71/95) of CC cycles. The median (minimum–maximum) number of follicles sized >15 mm in diameter on the day of hCG administration were 1 (0–4) and 1 (0–5) in the letrozole and CC groups, respectively. On the day of hCG administration, median serum E 2 concentrations in the letrozole and CC groups were statistically significantly different: 189 pg/mL (18–1,581 pg/mL) and 386 pg/mL (27–6,190 pg/mL), respectively. The median serum E 2 concentrations per follicle sized >15 mm in diameter on the day of hCG also statistically significantly differed between the letrozole and CC groups: 160 pg/mL (18–808 pg/mL) and 281 pg/mL (27–2,615 pg/mL), respectively. The median endometrial thickness on the day of hCG did not significantly differ between the CC and letrozole groups; it was 8 mm. Pregnancy was achieved in nine cycles (9.1%) of the letrozole group and in seven cycles (7.4%) of the CC group, which also was not a statistically significant difference. The aromatase inhibitor letrozole may be an acceptable alternative to CC as an ovulation-induction drug in patients with PCOS.