Background: Both obesity and sex hormones are known risk factors for postmenopausal breast cancer. Although adiposity and sex hormones have been studied in the past, previous reports in postmenopausal women have not been conducted under carefully controlled dietary conditions. In this study, we investigated the usefulness of body mass index (BMI) as a sufficient adiposity measurement to assess associations with sex hormone levels. Methods: This study was conducted as a cross-sectional analysis within the control segment (0 g alcohol group) of a randomized, crossover design, in which 51 postmenopausal women consumed 0 (control), 15 (one drink), and 30 (two drinks) g alcohol (ethanol)/d for 8 weeks each as part of a controlled diet. Dual-energy X-ray absorptiometry scans were administered to the women during the control (0 g alcohol) segment, and a blood sample was drawn at the end of that diet period for hormone analysis. Results: In multivariate analysis (adjusted for age, race, family history of breast cancer, parity, and menarche <12 years), women who were overweight or obese had significantly higher serum concentrations of estradiol, bioavailable estradiol, estrone, and estrone sulfate and lower sex hormone-binding globulin than normal weight women (all P < 0.05). In models adjusted for BMI and the covariates above, none of the dual-energy X-ray absorptiometry adiposity measures added further information (all P > 0.10) for these five analytes beyond that of BMI alone. Conclusions: In this population of postmenopausal women, under carefully controlled dietary conditions, we confirmed previous findings that higher levels of adiposity were associated with higher concentrations of estrogens and lower sex hormone-binding globulin, and we found that the use of the epidemiology-friendly BMI seems sufficient to assess associations with these hormone levels.
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