Abstract B113: Determinants of serum sex hormone binding globulin and testosterone in overweight and weight-reduced premenopausal women

Abstract

Abstract Introduction: Epidemiological studies have linked androgens and low sex hormone binding globulin (SHBG) with increased risk for breast cancer in premenopausal women. Obesity and the metabolic complications associated with increased adiposity have been shown to mediate both of these factors. The purpose of this study was to determine whether weight reduction through caloric restriction (CR), CR + aerobic exercise (CR+AE) or CR + resistance training (CR+RT) modifies serum total testosterone, bioavailable testosterone and SHBG. Methods: Participants were 138 healthy, over weight (BMI 27–79) premenopausal women not taking oral contraceptives randomized to CR, CR+AE or CR+RT in order to achieve normal body weight (BMI<25). Results: All three groups significantly reduced BMI from baseline to follow-up. There was no significant difference in adjusted mean BMI among the groups following weight loss. All three groups significantly increased SHBG (p<0.0001) and significantly decreased bioavailable testosterone (p<0.0001) from baseline to follow up. With all participants combined there was significant decrease in total testosterone as well as in the CR group (p≤0.05 for both). There was no difference in adjusted mean total testosterone, bioavailable testosterone and SHBG concentrations among the three groups following weight loss. Multiple linear regression models revealed that 64% of the variance in baseline SHBG was explained by age, intra-abdominal fat, bioavailable testosterone, insulin, and high density lipoprotein (HDL). After adjusting for baseline SHBG, 81% of the variance was explained by age, free testosterone and HDL in the weight reduced state. Twenty-three percent of the variance in baseline total testosterone was explained by age, estradiol, norepinephrine, low density lipoprotein (LDL) and leptin. After adjusting for baseline total testosterone, 58% of the variance was explained by age, estradiol and leptin in the weight reduced state. Conclusions: Testosterone, bioavailable testosterone and SHBG are highly influenced by obesity and can be modified through weight loss. Weight loss through CR or in combination with exercise achieves similar effects on testosterone and SHBG concentrations. The determinants of serum total testosterone and SHBG are different in the overweight and weight reduced state. Citation Information: Cancer Prev Res 2010;3(1 Suppl):B113.