Objective: To identify factors associated with serum estradiol (E2) levels among healthy postmenopausal women using hormone therapy (HT).
Methods: This is an unplanned post hoc analysis of data from ELITE (Early versus Late Intervention Trial with Estradiol), a randomized controlled trial of 1 mg oral E2 with or without vaginal progesterone in healthy early compared with late (<6 years compared with 10 or more years since menopause) postmenopausal women. We included results from visits when women reported at least 80% compliance with HT. Mixed-effects linear models identified factors associated with serum E2 levels while participants were taking HT, assessed every 6 months over a median follow-up of 4.8 years and adjusted for baseline E2 level, visit, and reduced E2 dose. Possible correlates evaluated included demographics, clinical characteristics, medication use, and biomarkers of liver and kidney metabolic function.
Results: The analysis included 2,160 E2 measurements in 275 postmenopausal women. Mean±SD age was 55.4±3.9 vs 64.4±5.5 years, and mean±SD time since menopause was 3.6±1.8 vs 16.0±5.6 years for early vs late postmenopausal women. Adjusted for pretreatment E2 level, visit, and reduced dose indicator, higher serum E2 levels were associated with higher body mass index (BMI), higher weight, surgical menopause, alcohol use, and antihypertensive medication use. Current and past smoking and antifungal medication use were associated with lower serum E2 levels. In the multivariable model, higher BMI and alcohol use were associated with higher serum E2 levels, whereas current and past smoking were associated with lower serum E2 levels. These factors were similar between early and late postmenopausal women.
Conclusion: Factors associated with serum E2 levels among postmenopausal women taking HT include BMI, alcohol use, and smoking. As serum E2 levels relate to HT effect, achievement of desirable E2 levels may be maximized through personalized intervention.
Clinical trial registration: ClinicalTrials.gov, NCT00114517.