FALSE: In the 1940s it was observed that castration reduced the incidence of prostate cancer. From this observation, it was extrapolated that testosterone must play a role in the pathophysiology of prostate cancer. The testicle produces several hormones other than testosterone, and it is now believed that the improvement seen in those patients was due to a decrease in estrogen production rather than testosterone. Prostate cancer is uncommon in young men, who generally have higher levels of testosterone, and becomes more prevalent with age, as testosterone levels fall. Over the past decade or so, there have been many investigations that have disproven the link between testosterone and prostate cancer.