TRT and Prostate Cancer: The 80-Year Myth

For over 80 years, one of the most persistent fears keeping men from treating their low testosterone has been the belief that testosterone causes prostate cancer. Doctors have repeated it. Patients have believed it. And millions of men with debilitating hypogonadal symptoms have suffered unnecessarily because of it.

The problem: this belief is based on a 1941 study of a single patient. The mountain of evidence accumulated since then tells a completely different story.

Key Takeaways

• The testosterone-prostate cancer link originated from Huggins' 1941 study involving just one patient
• The saturation model shows prostate tissue stops responding to testosterone above ~250 ng/dL
• The TRAVERSE trial (5,246 men, 4+ years) found no significant increase in prostate cancer with TRT
• A pooled analysis of 18 prospective studies found zero association between testosterone levels and prostate cancer risk
• Current AUA guidelines state there is no evidence linking TRT to prostate cancer development
• Active prostate cancer remains a contraindication -- the myth is about causation, not treatment of existing cancer

The Study That Started It All: Huggins, 1941

In 1941, Charles Huggins and Clarence Hodges published a landmark paper demonstrating that castration caused metastatic prostate cancer to regress, while estrogen treatment produced similar benefits. For this work, Huggins received the Nobel Prize in Medicine in 1966.

But the paper contained a second claim that would shape urology for decades: that administering testosterone caused prostate cancer to grow.

Here is the part nobody talks about: that conclusion was based on results from one patient.

A single man with metastatic prostate cancer received testosterone injections, and his acid phosphatase levels (a crude marker for prostate cancer activity at the time) rose. From this single observation, a generation of physicians concluded that testosterone fuels prostate cancer -- and that giving testosterone to any man was dangerous.

Why the Conclusion Was Wrong

Several problems with the original study:

• Sample size of one. A single case report became the foundation for a universal medical belief.
• The patient already had metastatic cancer. Giving testosterone to a man with advanced prostate cancer is fundamentally different from giving it to a healthy man with low testosterone.
• Acid phosphatase is a poor marker. It was the best available in 1941, but it is wildly imprecise compared to modern PSA testing.
• Confirmation bias. Huggins' castration results were genuinely revolutionary. The assumption that the reverse must also be true -- that adding testosterone must fuel cancer -- felt logical but was never properly tested.

As Abraham Morgentaler documented in his 2006 historical review, subsequent researchers who administered testosterone to men with prostate cancer found no progression in the majority of cases. Some patients even reported improvement in symptoms like bone pain. These contradictory results were largely ignored for decades.

The Saturation Model: Why More Testosterone Does Not Mean More Cancer

In 2009, Morgentaler and Traish published the saturation model, which fundamentally changed how researchers understand testosterone's effect on the prostate.

The model is straightforward: prostate tissue growth depends on androgen receptor (AR) binding. These receptors have a finite capacity. Once they are fully occupied -- which happens at surprisingly low testosterone levels -- additional testosterone has no further effect on prostate growth.

The saturation point is approximately 250 ng/dL (8.7 nmol/L).

This means:

• Below 250 ng/dL, small changes in testosterone dramatically affect prostate tissue. This is why castration (dropping testosterone to near zero) causes prostate cancer regression.
• Above 250 ng/dL, increasing testosterone from 300 to 500 to 800 ng/dL produces no meaningful additional prostate stimulation. The receptors are already fully bound.

Think of it like a sponge. A dry sponge absorbs water quickly with each drop. But once saturated, pouring more water on it does nothing -- it just runs off. The prostate's response to testosterone works the same way.

This explains a paradox that confused researchers for decades: if testosterone drives prostate cancer, why does prostate cancer become most common in older men, precisely when testosterone levels are lowest? The saturation model provides the answer -- prostate cancer development has nothing to do with testosterone levels in the normal or even supraphysiological range.

The clinical implications are significant. When a man with a testosterone level of 180 ng/dL starts TRT and rises to 600 ng/dL, his prostate tissue experiences meaningful androgen stimulation only during the transition from 180 to roughly 250 ng/dL. The additional increase from 250 to 600 ng/dL has no additional prostate-stimulating effect. This is why PSA rises modestly in the first few months of TRT and then plateaus -- the androgen receptors saturate quickly, and additional testosterone simply has nowhere to bind in prostate tissue.

The saturation model also explains why studies of men on TRT consistently fail to find increased prostate cancer rates. Most hypogonadal men starting TRT have baseline testosterone above the saturation point's lower bound, meaning their prostate tissue is already maximally stimulated before they ever receive their first injection.

What the Large Studies Actually Show

18 Prospective Studies: No Association

The Endogenous Hormones and Prostate Cancer Collaborative Group pooled data from 18 prospective studies -- 3,886 men with prostate cancer and 6,438 controls. Their conclusion: no association between serum testosterone concentrations and prostate cancer risk.

Not a weak association. Not a trend. Zero association. This applied to total testosterone, free testosterone, dihydrotestosterone (DHT), and every other androgen measured.

Meta-Analysis of TRT Studies

A 2014 systematic review and meta-analysis examined all available studies of TRT and prostate cancer outcomes. Across both short-term and long-term testosterone treatment, the odds ratios for prostate cancer did not reach statistical significance for any route of administration -- injections, gels, or pellets.

The TRAVERSE Trial: The Definitive Answer

The TRAVERSE trial is the largest and most rigorous study ever conducted on testosterone therapy safety. It enrolled 5,246 men aged 45-80 who had hypogonadism and either pre-existing cardiovascular disease or high cardiovascular risk. They were randomized to receive daily testosterone gel or placebo for a mean of 33 months, with some followed for over 4 years.

The prostate safety results, published in JAMA Internal Medicine in 2023:

• High-grade prostate cancer: 5 cases in the testosterone group vs. 3 in placebo (0.19% vs. 0.12%). Not statistically significant (HR 1.62, 95% CI 0.39-6.77, p = 0.51).
• Any prostate cancer: No significant difference between groups.
• Acute urinary retention: No significant difference.
• Prostate biopsies: No significant difference.
• Invasive surgical procedures: No significant difference.

Over 14,304 person-years of follow-up, testosterone therapy did not increase any measured prostate safety outcome.

This was not a small observational study. This was a $50+ million, multicenter, double-blind, placebo-controlled randomized clinical trial -- the gold standard of medical evidence. And it found no prostate cancer signal.

PSA Monitoring on TRT: What to Expect

Even though TRT does not cause prostate cancer, responsible monitoring is still important. Here is what the evidence shows about PSA changes on TRT:

Normal PSA Behavior on TRT

• Expect a modest increase. PSA typically rises 0.3-0.5 ng/mL in the first 3-6 months, then stabilizes.
• This is not cancer. The increase reflects normal prostate tissue responding to restored androgen levels -- similar to what happens when a dehydrated sponge absorbs water. It is reaching its normal state, not growing abnormally.
• PSA should plateau. After the initial adjustment period, PSA should remain stable. Continued upward trending is not typical of TRT alone.

When to Investigate Further

• PSA velocity greater than 0.75 ng/mL per year warrants further evaluation
• PSA doubling in less than 3 years requires investigation regardless of absolute value
• PSA above 4.0 ng/mL (or above age-adjusted thresholds) should prompt a urology referral
• Any rapid increase in the first 3-6 months beyond 1.0-1.5 ng/mL deserves a closer look

Recommended Monitoring Schedule

Timepoint	Action
Baseline (before TRT)	PSA, DRE, symptom assessment
3-6 months	Repeat PSA
12 months	PSA, DRE
Annually thereafter	PSA, DRE

If baseline PSA is above 3.0 ng/mL or there are other risk factors (family history, African American heritage), a urology consultation before starting TRT is appropriate.

When TRT Is Genuinely Contraindicated

Debunking the myth does not mean testosterone is safe for everyone. There are clear situations where TRT should be avoided:

Absolute contraindications:

• Active, untreated prostate cancer. While TRT does not cause prostate cancer, it may accelerate growth in men who already have it. Androgen deprivation remains a cornerstone of advanced prostate cancer treatment for exactly this reason.
• Metastatic prostate cancer. Huggins was right that castration helps metastatic disease regress. The error was extrapolating that to healthy men.

Situations requiring specialist oversight:

• History of treated prostate cancer. Some urologists now offer TRT to men with a history of successfully treated low-risk prostate cancer, particularly after radical prostatectomy with undetectable PSA. This is done on a case-by-case basis with close monitoring. Evidence is growing but still limited.
• Men on active surveillance for low-grade prostate cancer. A 2024 population-based analysis showed no increase in oncologic progression among men on active surveillance who received TRT, but this remains controversial and requires a shared decision with a urologist.

The key distinction: TRT does not cause normal cells to become cancerous. The concern is limited to men who already have cancer.

What Current Guidelines Say

The American Urological Association (AUA) guidelines on testosterone deficiency state:

"Clinicians should inform patients of the absence of evidence linking testosterone therapy to the development of prostate cancer."

This is as close to definitive as medical guidelines get. The AUA is not saying the evidence is unclear or that more research is needed. They are saying the evidence shows no link.

The Endocrine Society and the European Association of Urology have issued similar positions, all acknowledging that the historical fear was not supported by evidence.

The AUA does recommend that men with a known history of prostate cancer be counseled about the limited evidence in that specific population -- which is a reasonable and different question from whether TRT causes cancer in the first place.

It is worth noting how dramatically guidelines have shifted. In the early 2000s, many endocrinologists considered any prostate cancer history an absolute contraindication to TRT. By 2018, the AUA removed that blanket prohibition. By 2024, major urology conferences were debating whether TRT could be safely offered even to men on active surveillance for low-grade prostate cancer. The evidence has moved decisively in one direction -- toward safety -- and the guidelines have followed.

Practical Takeaways for Men Considering TRT

If you have been avoiding TRT because of prostate cancer fears:

1. The fear is based on outdated science. An 80-year-old study of one patient should not dictate your health decisions in 2026.
2. Get a baseline PSA and DRE before starting. This is standard practice and gives your clinician a reference point.
3. Monitor PSA at 3-6 months, then annually. A small rise is normal and expected. Rapid or sustained increases warrant investigation.
4. Know your family history. Having a first-degree relative with prostate cancer does not prevent you from using TRT, but it does mean more vigilant screening.
5. Work with a clinic that understands the current evidence. If your doctor refuses to prescribe TRT solely because of prostate cancer concerns, they may not be up to date on the last two decades of research. Consider a second opinion from a clinic that specializes in hormone therapy.

If you are already on TRT:

• Continue your monitoring schedule. The evidence is reassuring but not a reason to skip labs.
• Do not ignore urinary symptoms. BPH (benign prostate enlargement) can occur independently of cancer risk and may be affected by testosterone.
• Report any new lower urinary tract symptoms to your clinician.

The Bottom Line

The belief that testosterone causes prostate cancer is one of medicine's most enduring myths. It originated from a single patient observation in 1941, survived for 80 years on inertia and fear, and has been systematically dismantled by the saturation model, large prospective studies, meta-analyses, and the definitive TRAVERSE trial.

None of this means prostate monitoring is unnecessary. It means the reason for monitoring is vigilance -- not because TRT is dangerous, but because prostate cancer is common in aging men regardless of testosterone status, and catching it early matters.

If low testosterone is affecting your quality of life, prostate cancer fear -- based on one patient from 1941 -- should not be the reason you continue to suffer.

For more on how TRT works in your body, what to expect in your first month, or how to evaluate a TRT clinic, explore our other guides.

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References

1. Huggins C, Hodges CV. Studies on prostatic cancer: I. The effect of castration, of estrogen and of androgen injection on serum phosphatases in metastatic carcinoma of the prostate. 1941. J Urol. 2002;168(1):9-12. PMID: 12050481

2. Morgentaler A. Testosterone and prostate cancer: an historical perspective on a modern myth. Eur Urol. 2006;50(5):935-939. PMID: 16875775

3. Morgentaler A, Traish AM. Shifting the paradigm of testosterone and prostate cancer: the saturation model and the limits of androgen-dependent growth. Eur Urol. 2009;55(2):310-320. PMID: 18838208

4. Endogenous Hormones and Prostate Cancer Collaborative Group. Endogenous sex hormones and prostate cancer: a collaborative analysis of 18 prospective studies. J Natl Cancer Inst. 2008;100(3):170-183. PMID: 18230794

5. Cui Y, et al. The effect of testosterone replacement therapy on prostate cancer: a systematic review and meta-analysis. Prostate Cancer Prostatic Dis. 2014;17(2):132-143. PMID: 24445948

6. Lincoff AM, et al. Cardiovascular safety of testosterone-replacement therapy. N Engl J Med. 2023;389(2):107-117. PMID: 37326322

7. Bhasin S, et al. Prostate safety events during testosterone replacement therapy in men with hypogonadism: a randomized clinical trial. JAMA Intern Med. 2023;184(2):173-182. PMID: 38150256

8. Mulhall JP, et al. Evaluation and management of testosterone deficiency: AUA guideline. J Urol. 2018;200(2):423-432. PMID: 29601923