Body size and composition, physical activity and sedentary time in relation to endogenous hormones in pre- and post-menopausal women: findings from the UK Biobank

Anthropometric and lifestyle factors may influence cancer risks through hormonal changes. We investigated cross-sectional associations between body size and composition, physical activity and sedentary time and serum concentrations of oestradiol (pre-menopausal women only), testosterone, SHBG (sex hormone binding globulin) and IGF-1 (insulin-like growth factor-1) in 20,758 pre-menopausal and 71,101 post-menopausal women in UK Biobank. In pre-menopausal women, higher BMI (body mass index) was associated with a lower concentration of total oestradiol (15% difference in the highest vs. lowest BMI group) and a higher concentration of calculated free oestradiol (22%). In both pre- and post-menopausal women, higher BMI was associated with higher concentrations of total and calculated free testosterone (pre-menopausal 29% and 113%, postmenopausal 39% and 126%, respectively) and lower concentrations of SHBG and IGF-1 (premenopausal 51% and 14%, post-menopausal 51% and 12%, respectively). Similar associations were observed with waist to height ratio, waist to hip ratio and body or trunk fat mass. Self-reported physical activity was associated with somewhat lower concentrations of total and calculated free testosterone (pre-menopausal 10% difference (free testosterone), post-menopausal 5% and 11% difference respectively in the most vs. least active group) and a higher concentration of SHBG (premenopausal 11%, postmenopausal 10%), and the opposite was true for self-reported sedentary time. The associations were slightly stronger with accelerometer-measured physical activity, but were attenuated after adjustment for BMI. Overall, this study confirms strong associations of hormones and SHBG with anthropometric factors. The associations with physical activity and sedentary time were at most modest