ARS | Publication request: Usefulness of Body Mass Index (BMI) as a Sufficient Adiposity Measurement for Sex Hormone Concentration Associations in Postmenopausal Women

Submitted to: Cancer Epidemiology Biomarkers and Prevention
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 10, 2006
Publication Date: December 1, 2006
Citation: Mahabir, S., Baer, D.J., Johnson, L., Hartman, T., Dorgan, J., Campbell, W., Judd, J.T., Clevidence, B.A., Taylor, P. 2006. Usefulness of body mass index (BMI) as a sufficient adiposity measurement for sex hormone concentration associations in postmenopausal women. Cancer Epidemiology Biomarkers and Prevention. 15(12):2502-2507.

Interpretive Summary: Obesity and certain hormones, such as estrogens, are risk factors for breast cancer in postmenopausal women. The distribution of body fat may be an additional risk factor for breast cancer in this group of women. However, the relationship between body fat distribution and sex hormone concentrations is not known. The goal of this study was to determine the contributions of adipose tissue distribution and body size, body mass index (BMI), in predicting sex hormone levels in postmenopausal women. Fifty-one postmenopausal women consumed a controlled diet for 8 weeks. The diet provided about 15%, 50%, and 35% of energy from protein, carbohydrate, and fat, respectively. Dual energy x-ray absorptiometry (DEXA) scans were administered to the women and a blood sample was collected for hormone analysis. DEXA fatness measures (i.e., total body fat, trunk fat, leg fat, and arm fat) were highly correlated and increasing levels of DEXA fatness and BMI were associated with significant, and similar increases in serum estradiol, bioavailable estradiol, estrone, and estrone sulfate, and a decrease in serum sex hormone binding globulin (SHBG). In this controlled study, we found that increasing levels of body fatness were associated with higher blood levels of estrogens and lower levels of SHBG. DEXA total and regional fatness predicted serum estrogen concentrations in a comparable manner to BMI in this population of women. These findings are important to physicians, allied health care providers, and women at risk for breast cancer who may be able to reduce their risk through changes in their body fat.

Technical Abstract: Obesity and sex hormones such as estrogens are known risk factors for postmenopausal breast cancer. There is an increasing argument that regional adiposity such as abdominal adiposity measured by waist-to-hip ratio may be an additional risk factor for breast cancer in postmenopausal women. However, the effect of regional adiposity distribution on sex hormone concentrations is unknown. The goal of this study was to assess and compare the contributions of regional adipose tissue distribution and BMI in predicting sex hormone levels in postmenopausal women. This study was conducted as a cross-sectional analysis within the control segment of a randomized, crossover design in which postmenopausal women (n=51) consumed 0 (control), 15 (1 drink), and 30 (2 drinks) g alcohol (ethanol)/day for 8 weeks each as part of a controlled diet. The women ate a controlled diet for 8 weeks, which provided about 15%, 50%, and 35% of energy from protein, carbohydrate, and fat, respectively. Dual energy x-ray absorptiometry (DEXA) scans were administered to the women during the 0 g alcohol treatment, and a blood sample was drawn at the end of that diet period for hormone analysis. DEXA adiposity (i.e., total body fat, trunk fat, leg fat, and arm fat) were highly correlated and increasing levels of DEXA adiposity and BMI were all associated with significant, and similar increases in serum estradiol, bioavailable estradiol, estrone, and estrone sulfate, and a decrease in serum sex hormone binding globulin (SHBG). In this controlled study, we found that increasing levels of adiposity were associated with increased concentrations of estrogens and decreased concentrations of SHBG. DEXA total and regional adiposity measures predicted serum estrogen concentrations in a comparable manner to BMI in this population of women.