Testosterone supplements, rats, and risk for prostate cancer in healthy, aging men


The “New” Prostate Cancer InfoLink has long argued that the use of testosterone supplements by otherwise healthy men as they age (as a way to try to maintain the vigor and libido of their youth) comes with risks, and that one of those risks is the risk for a diagnosis of prostate cancer.

Testosterone replacement therapy (TRT), in various forms, has been approved by the U.S. Food and Drug Administration only for the management of hypogonadism (low testosterone levels compared to the norm in a specific age group of men) and not for the very normal decrease in testosterone levels observed as we age. Furthermore, risk for prostate cancer already goes up significantly as we pass the age of about 55 or 60, and so if taking testosterone supplements increases the risk of a diagnosis of prostate cancer, one is only increasing the risk for something that most of us are already hoping we don’t have to deal with as we get older!

Now it would be a mistake to think that we “know for certain” that TRT in normal, otherwise healthy, but aging men is associated with a major and clinically significant increase in risk for prostate cancer. There are certainly suggestions that this is the case, but the case is not closed (yet). On the other hand, a new paper by Bosland in the journal Epidemiology has now reported that TRT is associated with an increase in risk for prostate cancer tumors in rats. The paper is also discussed on the MedPageToday web site

Bosland has shown that when his laboratory rats were treated using slow-release implants of testosterone:

  • Circulating levels of serum testosterone increased in a dose-related fashion (with or without a preceding single injection of the carcinogen N-nitroso-N-methylurea or MNU).
  • If there was no pre-injection of MNU, testosterone-induced prostate cancers in 10 to 18 percent of the rats.
  • If the rats were pre-injected with MNU,
    • Prostate cancer was observed in 50 to 71 percent of the rats.
    • There was a very steep dose response (with a 50 percent rate of prostate cancer tumor incidence even at a dose of testosterone so low that it didn’t increase circulating testosterone levels).
  • If there was no pre-injection of MNU and no testosterone treatment, the rats did not get prostate cancer.
  • If there was no pre-injection of MNU but there was treatment with testosterone alone then the rats demonstrated
    • A low incidence of prostate cancer
    • An increase in risk for tumors at other sites (particularly malignant tumors).

Borland concludes that testosterone is “a weak complete carcinogen and a strong tumor promoter for the rat prostate in this study” and goes on to state that, “These findings have potential significant public health implications for the use of testosterone therapy in men.”

Don’t tell us that you weren’t warned! Our view is that not taking testosterone supplements helps otherwise healthy men to limit their risk for a diagnosis of prostate cancer.

7 Responses

  1. Normal serum testosterone levels have nothing to do with non-metastatic prostate cancer. The contrary, low testosterone level, has a higher incidence of prostate cancer occurrence than the general population.

    Suggested reading; just about anything by Dr. Morgenthaler. He is a pioneer in the field. Too much to go into in this space. I have read his papers, and he totally debunks the faulty initial “science” concerning the testosterone/prostate cancer connection.

  2. Dear Walt:

    With the greatest respect, Dr. Morgenthaler’s research is not anything like as definitive as you would like to believe. His is one of many opinions about all of this.

    I would also point out that the paper referenced above is not about men with hypogonadism (i.e., “real” low testosterone levels compared to the age-related norms). Men with truly hypogonadal conditions may well be at greater risk for prostate cancer, but that does not necessarily translate into the idea that the perfectly normal reduction in serum T levels as we age is in any way associated with an increase in risk for prostate cancer.

  3. Understood. There’s low T, and then there’s hypogonadism. Low-T men, who are just low but within normal range, ought to consider natural ways of upping their T before going on TrT.

    That being said, chronically low T causes more harm than any indolent PCa ever will ….

  4. Also, it is at least logical that lowering T with age places us more at risk for prostate cancer. That is, after all, when it tends to occur. As they say, if all men lived to be 100 years old, near 100% of us would have some prostate cancer

    Think about it ….

  5. Walt:

    Actually your second hypothesis is not necessarily logical at all. Risk for almost all cancers increases with age because all of our body’s functions start to become less efficient … including our immune systems. In other words, there is no specific reason to think that as our serum T levels decline with age, that is what causes our risk for prostate cancer to rise. Might it be contributory? Perhaps. But there are a whole host of other possible reasons for this effect too.

  6. We are forgetting the prostate cancer patient that has had prostate cancer, had treatment, and has shown zero PSA for several years. If they are unfortunate enough to have hypogonadism, testosterone treatment is a possible return to quality of life. Then the questions become: Are they free of cancer? If so, why not? and Are we forgetting the post-cancer patient in this debate.

  7. Dear Alan:

    There was no intention to “forget” the post-treatment patient in this debate. The original paper was exclusively about the use of TRT by healthy, aging men, and the associated risk for onset of prostate cancer among such men. The potential for use of TRT among men who have been diagnosed with prostate cancer and subsequently have low serum T levels is a quite different issue (with its own set of controversies). This is also an area where the work of Dr. Morgenthaler (mentioned above) becomes more relevant.

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