Associations between testosterone levels and incident prostate, lung, and colorectal cancer. A population-based study.

BACKGROUND The relationship between testosterone and cancer is relatively unexplored. We sought to examine whether testosterone and related hormones are associated with incident prostate, lung, and colorectal cancer. METHODS This was a population-based cohort study. Demographic and clinical predictors of cancer, and testosterone, sex hormone-binding globulin (SHBG), and luteinizing hormone (LH) were measured between 2001 and 2004 in 3,635 community-dwelling men aged 70 to 88 years (mean 77 years). Cancer notifications were obtained via electronic record linkage until December 31, 2010. RESULTS During a mean follow-up period of 6.7 ± 1.8 years, there were 297, 104, and 82 cases of prostate, colorectal, and lung cancer. In adjusted competing risks proportional hazards models, each one SD increase in free testosterone was associated with a 9% increase in prostate cancer risk (95% confidence interval [CI], 1.00-1.18), but other hormones were not significantly associated. No significant associations were observed between hormonal parameters and colorectal cancer. Higher total testosterone was associated with lung cancer. Compared with the mean of 15 nmol/L, men with levels of 20 nmol/L were 1.38 times more likely to be cases (95% CI, 1.21-1.57), whereas those with levels of 30 nmol/L were 3.62 times more likely to be cases (95% CI, 2.53-5.18). Higher free testosterone was also associated with lung cancer, though SHBG and LH were not. Associations were maintained after exclusion of current smokers. CONCLUSIONS Higher free testosterone was associated with incident prostate cancer. Higher testosterone levels may also be associated with lung cancer. IMPACT Further studies should investigate whether these risks apply to men receiving testosterone therapy.