Sex hormones, SHBG and risk of colon and rectal cancer among men and women in the UK Biobank

Background: Experimental studies have suggested a role for sex hormones in the etiology of colorectal cancer (CRC) but epidemiological data are inconclusive. Methods: We examined the associations of testosterone, estradiol, and sex hormone binding globulin (SHBG), with risk of CRC (n = 3,247) in 206,508 men and 219,106 women enrolled in the UK Biobank. Participants were followed for a median of 7.1 years. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95 % confidence intervals (CIs) for CRC risk. Results: In men, in multivariable adjusted models testosterone and SHBG were not associated with CRC. Among men in the highest tertile of physical activity, SHBG was inversely associated with risk (HR_q5 vs_{. q1} 0.75, 0.56−0.99,). In women, testosterone and SHBG were not associated with CRC risk. There were no differences in the associations between testosterone, SHBG and CRC risk in the analyses stratified by menopausal status. We did not observe an association between estradiol and CRC risk; however, given the limited number of individuals with detectable values of estradiol (13.2 % of the total sample) we are unable to draw a firm conclusions regarding this association. Conclusion: The results of this study did not provide support for associations of sex hormones and SHBG with CRC risk.