A multicenter randomized placebo-controlled trial evaluating daidzein-rich isoflavone aglycones in endometriosis-associated dysmenorrhea

Takaoka O, Osamu Takaoka, Okimura H, Hiroyuki Okimura, Tarumi Y, Yosuke Tarumi, Kawamata M, Mari Kawamata, Fumitake Ito, Ito F, Akemi Koshiba, Koshiba A, Kusuki I, Izumi Kusuki, Kitawaki J, Jo Kitawaki, Mori T, Taisuke Mori
In: Research Square · 2026 · doi:10.21203/rs.3.rs-9799296/v1 · W7167587364
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Abstract

Abstract Background Endometriosis-associated dysmenorrhea is commonly managed with hormonal therapies that suppress ovulation, limiting their use in women desiring fertility. Daidzein-rich isoflavone aglycones (DRIAs), a food-derived compound with estrogen receptor-mediated anti-inflammatory and proliferative effects, may represent a provide a novel therapeutic option. Methods This multicenter, randomized, double-blind, placebo-controlled trial enrolled Japanese women aged 20–50 years with endometriosis-associated dysmenorrhea (visual analog scale (VAS) ≥ 20). Participants were randomized to receive DRIAs (30 mg/day) or placebo for 4 months. The primary endpoint was change in dysmenorrhea VAS score, analyzed using a baseline-adjusted linear mixed model. Secondary outcomes included changes in endometriotic cyst diameter, other pain symptoms, and safety parameters. Results: A total of 81 participants were randomized, and 71 were included in the modified intention-to-treat analysis. Dysmenorrhea VAS scores improved significantly over time in both groups (p < 0.001). although the group-by-time interaction was not statistically significant, a significant between-group difference favoring DRIAs was observed at Month 3 (− 13.53, 95% CI − 23.8 to − 3.22; adjusted p = 0.041). The direction of effect consistently favored DRIAs across time points. The responder rate (≥ 30% reduction at Month 4) was higher in the DRIAs group (73.5% vs 56.8%), although not statistically significant. No serious adverse events or clinically relevant laboratory abnormalities were observed. Conclusions: DRIAs may provide a safe, non-hormonal therapeutic option for endometriosis-associated dysmenorrhea without suppression of ovarian function. The observed magnitude and consistency of pain reduction suggest a clinically meaningful effect, supporting further evaluation in adequately powered studies.

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