One of the most commonly cited side effects of hormone replacement therapy as a cure for low testosterone levels in men is an increased risk of prostate cancer. However, as with the Million Woman Study that linked HRT and breast cancer, the evidence supporting this belief is outdated and probably false. In fact, according to some modern research, low testosterone levels are actually a risk factor for male cancers.
The origins of the theory that testosterone replacement increased the risk of prostate cancer can be traced back to research conducted at the University of Chicago in the 1940s by a group led by urologist Charles Huggins. Based on experiments done first in dogs and then humans, Huggins’s group concluded that prostate cancer was dependent on androgens: When testosterone levels were high, the cancer got worse, but when levels fell, the cancer shrunk. Huggins’s theory led to surgical castration (removal of the testicles) becoming the standard treatment for prostate cancer due to the resulting drop in testosterone. Huggins received a Nobel Prize in 1966 for these contributions to medical research.
Huggins’s findings led scientists and physicians to believe for many years that testosterone levels and the occurrence of prostate cancer were related, despite the fact that his experiments did not test or prove this and were limited to a small number of subjects from proof. This made medical professionals skeptical of hormone replacement therapy, fearing it could lead to the development of prostate cancer. Many avoided prescribing HRT, despite its benefits.
As time went on, more research was done and studies showed that men with low testosterone levels appeared to develop prostate cancer at a higher than average rate, and that testosterone only caused the progression of prostate cancer in men that had been neutered, and not in men who still naturally produced testosterone. The alleged link between testosterone and prostate cancer had to be re-examined.
Eventually, the medical community began to change its tune as new evidence was presented to it. Several studies conducted in the 2000s, including those published by the New England Journal of Medicine and the Mayo Clinic, showed no correlation between elevated testosterone levels and prostate cancer. Separate studies by Abraham Morgentaler, a leading physician in the field, showed that increased testosterone levels in men already diagnosed with prostate cancer did not lead to further progression of the disease, and that men in the lower range of Testosterone levels actually have a higher risk of developing prostate cancer than men with higher amounts. It is now clear that the relationship between testosterone and prostate cancer was misunderstood for much of the 20th century, and that hormone replacement as a means of supplementing low testosterone levels in men will not cause the disease.
So if you are a man who suspects that you may have low testosterone and is considering hormone replacement therapy, you can rest easy. HRT will not give you prostate cancer; in fact, it could help prevent it.