Intra-abdominal adipose tissue is independently associated with sex-hormone binding globulin in premenopausal women

Lower serum concentrations of sex-hormone binding globulin (SHBG) are associated with increased risk for several obesity-related diseases in women including hormone-sensitive cancers, type 2 diabetes, metabolic syndrome, and cardiovascular disease. Previous investigations have reported that body composition, specifically central obesity, and/or higher insulin concentrations are key factors associated with lower SHBG in overweight and obese women; however, these studies were limited by their cross-sectional design. We hypothesized that intra-abdominal adipose tissue (IAAT), a fat depot linked with an abnormal metabolic profile, is inversely and independently associated with SHBG. Therefore, we determined the longitudinal associations among SHBG, insulin, and IAAT in 107 premenopausal women enrolled in a weight loss study. Overweight (BMI 27-30 kg/m(2)) women were weight reduced until BMI of ≤ 24 was achieved. Body composition and IAAT were measured at baseline and after weight loss with dual-energy X-ray absorptiometry and computed tomography, respectively. Serum concentrations of insulin and SHBG were determined. Paired t-test showed that insulin and IAAT decreased significantly and SHBG increased significantly following weight loss (P < 0.0001 for all). Simple correlations from baseline showed no association with insulin and SHBG (r = -0.142, P = 0.143) and a significant inverse association between IAAT and SHBG (r = -0.43, P < 0.0001). Repeated measures mixed-model showed that after adjusting for age and time (weight loss), IAAT was significantly inversely associated with SHBG (P = 0.0002) and there was no association with insulin and SHBG (P = 0.180). We conclude that SHBG concentrations are influenced by IAAT and not insulin in premenopausal women.