Effectiveness of letrozole in pituitary downregulated normogonadotrophic young women with an initial poor response

It has been reported that 10 to 15% of young normogonadotrophic women show suboptimal response to standard long protocols. Letrozole (LE), an aromatase inhibitor, was shown to improve ovarian sensitivity to follicle stimulating hormone (FSH) and follicular response to gonadotrophin treatment in poor ovarian response patients. We reasoned that it might be possible to utilize LE in young normogonadotrophic patients with unexpected hypo-response in standard gonadotropin-releasing hormone agonist long protocol. A total of 652 patients defined as normogonadotrophic patients with unexpected hypo-response were divided into 2 groups, the +LE group and the +Gn group. +LE group: A fixed daily dose of 2.5 mg of LE was added on day 8 of stimulation. +Gn group: A fixed daily dose of 75 U of human menopausal gonadotrophin was added on day 8 of stimulation. The primary outcome measures were the number of oocytes obtained, fertilization rate, days of stimulation, and total FSH dosage. The secondary outcome measures were the implantation rate and ongoing pregnancy rate. There were no significant differences in the clinical and hormonal characteristics between the 2 groups. A shorter duration of stimulation and a lower dosage of recombinant FSH consumption on the day of human chorionic gonadotropin administration were all observed in the +LE group. Patients who received LE therapy showed a higher number of oocytes obtained and significantly higher fertilization rates. The implantation rate and ongoing pregnancy rate were comparable in both groups. LE significantly improves the number of oocytes obtained in patients with suboptimal response to standard gonadotropin-releasing hormone agonist long protocol.