The aromatase inhibitor letrozole increases the concentration of intraovarian androgens and improves in vitro fertilization outcome in low responder patients: A pilot study

To evaluate the impact of aromatase inhibitors as adjuvant treatment in IVF cycles on intraovarian androgens and cycle outcome. Observational, pilot study. University-affiliated IVF unit. One hundred forty-seven low responder patients with a previous canceled IVF cycle; 71 patients were treated with letrozole 2.5 mg plus a high-dose FSH/hMG-antagonist regimen, and 76 patients were similarly treated but letrozole was not employed. In vitro fertilization treatment with an antagonist FSH/hMG protocol with or without letrozole was administered during the first 5 days of stimulation; hormones were evaluated in both serum and follicular fluid. Number of oocytes retrieved, fertilization rate, implantation rate, and pregnancy rate; androstenedione, T, E 2, and P values in serum and follicular fluid. Letrozole-treated patients showed significantly higher levels of follicular fluid T and androstenedione (80.3 vs. 43.8 pg/mL and 57.9 vs. 37.4 mg/mL, respectively). Similarly, these patients had a higher number of oocytes retrieved (6.1 vs. 4.3) and a higher implantation rate (25% vs. 9.4%) despite similar doses of FSH/hMG (3,627 vs. 3,804 IU). Adding 2.5 mg of letrozole to a high-dose FSH/hMG antagonist protocol increases intraovarian androstenedione and T concentration and improves IVF cycle outcome in poor responder patients.