Vaginal Lactobacillus iners Abundance Predicts Response to Local Estrogen Therapy in Postmenopausal Women with Genitourinary Syndrome of Menopause

Genitourinary syndrome of menopause (GSM) is a common chronic condition in postmenopausal women, yet biomarkers predicting response to local estrogen therapy remain insufficiently defined. In this prospective study, 216 postmenopausal women with GSM received local estradiol vaginal tablet therapy for 12 weeks. Baseline assessments included symptom evaluation, vaginal pH, vaginal maturation index (VMI), and quantitative real-time PCR measurement of six target microorganisms. Treatment response was defined as an improvement of at least 2 points in the most bothersome symptom (MBS) score. After 12 weeks, MBS score, vaginal pH, and VMI improved significantly, with increased abundance of L. crispatus, L. jensenii, and L. gasseri and decreased abundance of L. iners, Gardnerella, and Candida. Overall, 128 of 216 women responded (59.3%; 95% CI, 52.6-65.6%). Higher baseline L. iners abundance was independently associated with a lower probability of response (adjusted RR per log10-unit increase, 0.82; 95% CI, 0.70-0.95), with the highest tertile showing a lower response likelihood than the lowest (RR, 0.71; 95% CI, 0.54-0.93). These findings suggest that L. iners may be a promising candidate microbial marker for pretreatment risk stratification, although external validation is needed before clinical application.