Unit of Environmental Epidemiology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Obesity (Silver Spring). 2012 May;20(5):1088-95. doi: 10.1038/oby.2011.383. Epub 2012 Jan 12.
Being overweight or obese increases the risk of postmenopausal breast cancer. A potential reason may be the frequently observed positive association of BMI with endogenous sex hormones and its negative association with sex hormone-binding globulin (SHBG). The purpose of this study was to investigate whether a woman's body fat distribution shows a BMI-independent association with these breast cancer-related biomarkers. Performing cross-sectional analyses among 1,180 postmenopausal women, we assessed whether associations of surrogates for an abdominal (waist circumference; waist-to-hip ratio, WHR) and gluteofemoral (hip circumference) fat distribution with estrone, total and free estradiol, androstenedione, total and free testosterone, and SHBG changed after adjustment for, or stratification by, BMI. All anthropometric measures were positively associated with estrogens and free testosterone, and negatively with SHBG. After adjustment for BMI, associations of free estradiol, free testosterone, and SHBG with both waist circumference and WHR remained significant, but all initially significant associations with hip circumference were abolished. In stratified analyses, waist circumference and WHR correlated with free estradiol, free testosterone, and SHBG in women with a BMI < 30 kg/m(2) but not in women with a BMI ≥ 30 kg/m(2). The latter suggests that in obese women, a possibly unique effect of abdominal fat on these biomarkers may be masked by the already large amount of overall body fat. On the whole, our results indicate that waist circumference and WHR, but not hip circumference, are associated with SHBG and SHBG-related sex hormones (free estradiol and free testosterone) independently of BMI.
超重或肥胖会增加绝经后乳腺癌的风险。一个潜在的原因可能是 BMI 与内源性性激素经常观察到的正相关，以及与性激素结合球蛋白 (SHBG) 的负相关。本研究旨在探讨女性体脂分布是否与这些与乳腺癌相关的生物标志物存在 BMI 无关的关联。在 1180 名绝经后妇女中进行横断面分析，我们评估了腹部（腰围；腰臀比，WHR）和臀股部（臀围）脂肪分布的替代指标与雌酮、总雌二醇、游离雌二醇、雄烯二酮、总睾酮和 SHBG 的关联是否在调整 BMI 后或按 BMI 分层后发生变化。所有人体测量指标均与雌激素和游离睾酮呈正相关，与 SHBG 呈负相关。在调整 BMI 后，腰围和 WHR 与游离雌二醇、游离睾酮和 SHBG 的关联仍然显著，但与臀围的所有最初显著关联均被消除。在分层分析中，腰围和 WHR 与 BMI<30kg/m(2)的女性的游离雌二醇、游离睾酮和 SHBG 相关，但与 BMI≥30kg/m(2)的女性无关。后者表明，在肥胖女性中，腹部脂肪对这些生物标志物的可能独特影响可能被已经大量的总体体脂所掩盖。总的来说，我们的结果表明，腰围和 WHR 与 SHBG 以及与 SHBG 相关的性激素（游离雌二醇和游离睾酮）独立于 BMI 相关，而臀围则不相关。
