Impact of Letrozole Starting Dose on Endometrial Thickness in Ovulation Induction for PCOS

Open Access

Abstract

Background: PCOS is a common cause of anovulatory subfertility, and letrozole is widely used as first-line ovulation induction. Beyond ovulation, adequate endometrial thickness is important for implantation, and dose-related effects on endometrial development remain uncertain across protocols. Methods & Materials: This comparative prospective study was conducted at the Department of Obstetrics and Gynecology, BIRDEM General Hospital, from June 2023 to January 2025. Data were recorded in a structured CRF and analyzed using IBM SPSS Statistics; p<0.05 was considered significant. Results: Baseline characteristics did not differ significantly between groups in terms of age, body mass index (BMI), subfertility type, or duration. On cycle day 12, endometrial thickness was significantly greater in the letrozole 7.5 mg group compared to the 5 mg group, with mean values of 8.20 ± 1.99 mm and 6.45 ± 2.40 mm, respectively (p=0.001). The proportion of participants with endometrial thickness ≥8 mm was also higher in the 7.5 mg group (60.0%) than in the 5 mg group (37.5%; p=0.044). Among women with a dominant follicle, the proportion achieving ≥8 mm was similar between groups (88.9% vs 82.4%; p=0.66), although mean thickness remained higher with 7.5 mg (9.54 ± 0.80 mm vs 8.96 ± 0.74 mm; p=0.038). Both groups demonstrated significant increases in endometrial thickness from baseline to day 12 (p<0.001). Conclusion: A 7.5 mg starting dose of letrozole resulted in a thicker endometrium by day 12, with a greater proportion of women achieving an endometrial thickness (ET) of at least 8 mm compared to the 5 mg dose in polycystic ovary syndrome (PCOS) ovulation induction.