For decades, one assumption quietly blocked millions of men from a treatment that could restore their energy, protect their heart, and give them back their quality of life.

That assumption: testosterone feeds prostate cancer. It came from a 1941 study by Dr. Charles Huggins, who showed that removing testosterone caused advanced prostate cancer to regress. The medical community drew what seemed like a logical conclusion if less testosterone shrinks cancer, more testosterone must grow it. That inference shaped clinical practice for sixty years.

It was never actually proven. The research that has accumulated since tells a fundamentally different story. Landmark trials  including the largest randomized controlled study on testosterone therapy ever conducted have directly challenged the assumption that guided half a century of medicine. For most men, properly managed TRT does not meaningfully increase prostate cancer risk. In fact, the data points in the opposite direction. This guide breaks down what the science actually shows the original myth, the paradigm shift, the 2023 TRAVERSE trial findings, what TRT does to PSA levels, and who genuinely needs to be cautious.

What Is Testosterone Replacement Therapy (TRT)?

Testosterone replacement therapy is a medically supervised treatment for hypogonadism a clinical condition where the body fails to produce adequate levels of testosterone. It is not a performance drug or an anti-aging shortcut. It is hormone correction.

The goal of TRT is to restore testosterone to the normal physiological range of 300–1,000 ng/dL the level a healthy adult male should naturally maintain. When testosterone falls below that threshold, the downstream effects are significant: chronic fatigue, muscle loss, cognitive fog, low libido, depression, and increased cardiovascular risk.

TRT is delivered through several methods intramuscular injections, subcutaneous injections, topical gels and creams, transdermal patches, and implantable pellets. Each method carries a different absorption profile and hormonal pattern, which a qualified physician calibrates to your specific physiology and health goals.

What TRT is not: a one-size-fits-all prescription handed out without evaluation. Proper TRT begins with comprehensive lab work — total testosterone, free testosterone, LH, FSH, estradiol, PSA, hematocrit, and metabolic panels — and continues with regular monitoring throughout treatment. Understanding how TRT works at the hormonal level is essential context before evaluating any of its risks — including the prostate question this article addresses directly.

The Saturation Model: The Research That Changed Everything

The scientific challenge to the Huggins hypothesis came most prominently from Harvard urologist Dr. Abraham Morgentaler, whose research beginning in the 1990s introduced what is now known as the Saturation Model of testosterone and prostate tissue.

Morgentaler’s work demonstrated that androgen receptors in prostate tissue become fully saturated at relatively low testosterone concentrations — approximately 120 ng/dL in most men. Below that threshold, adding testosterone does stimulate prostate tissue growth. But above it — which encompasses the entire normal physiological range — additional testosterone has no further stimulatory effect on the prostate. The receptors are already fully occupied.

This is not a minor technical distinction. It is a fundamental reframing of the entire risk model. It explains why castrate-level testosterone causes prostate cancer to regress (the tissue is deprived of a signal it needs), while normal and high-normal testosterone levels do not cause cancer to grow (the receptors are already saturated). The dose-response relationship that the original fear assumed simply does not exist above the saturation threshold.

Morgentaler’s research, published across multiple peer-reviewed journals, demonstrated that men with low testosterone actually had higher rates of high-grade prostate cancer on biopsy than men with normal levels — directly reversing the expected relationship if the old hypothesis were true. His findings, replicated and built upon by subsequent research, laid the groundwork for a complete revision of how medicine thinks about testosterone and prostate risk.

What the 2023 TRAVERSE Trial Actually Proved

The most definitive evidence on TRT and prostate safety came from the TRAVERSE (Testosterone Replacement therapy for Assessment of long-term Vascular Events and efficacy Response) trial, published in the New England Journal of Medicine in 2023. This was the largest randomized controlled trial ever conducted on testosterone therapy — 5,246 men aged 45–80 with confirmed hypogonadism and existing or high-risk cardiovascular disease, followed for a median of 33 months.

The trial was designed primarily to assess cardiovascular safety, but its prostate findings were equally significant. Key results:

• No statistically significant increase in prostate cancer incidence in the testosterone group compared to placebo
• No significant difference in high-grade prostate cancer between groups
• Rates of prostate-related adverse events were comparable across treatment and control groups

This was not a small observational study. This was a rigorously controlled, double-blind, placebo-controlled trial with over five thousand participants and nearly three years of follow-up. Its prostate safety data represents the strongest evidence the field has ever produced — and it aligns with what the Saturation Model predicted: properly dosed TRT, calibrated to restore physiological testosterone levels, does not meaningfully increase prostate cancer risk in men without pre-existing disease. The American Urological Association (AUA) updated its clinical guidelines to reflect this evolving evidence, acknowledging that testosterone therapy is not contraindicated in men with well-treated, low-risk prostate cancer in select cases a position that would have been unthinkable in prior decades.

TRT and PSA: What to Expect

Prostate-specific antigen (PSA) is a protein produced by prostate tissue, and elevated PSA levels can indicate prostate cancer, BPH, or inflammation. It is a standard monitoring marker for men on TRT, and understanding how TRT affects it is essential for both patients and physicians.

Here is what the evidence shows:

Short-term PSA increase is normal and expected: When testosterone levels rise after starting TRT, PSA often increases modestly — typically in the range of 0.3 to 0.5 ng/mL within the first 3–6 months. This reflects the prostate responding to normalized androgen stimulation, not cancer developing. It is not cause for alarm in isolation.

The increase plateaus: After the initial adjustment period, PSA typically stabilizes. Men on long-term TRT do not show continuously rising PSA trajectories — they show a one-time normalization followed by stable readings, consistent with what the Saturation Model predicts.

Red flags that warrant investigation: A PSA increase of more than 1.4 ng/mL from baseline within the first year of TRT, or a confirmed velocity of more than 0.4 ng/mL per year during treatment, should prompt urological evaluation — not automatic TRT discontinuation, but thorough clinical assessment.

Baseline PSA testing before starting TRT and regular monitoring every 3–6 months in the first year is standard protocol at every reputable clinic. You can learn more about how to test testosterone and the full panel of markers that should be monitored throughout treatment.

TRT and Benign Prostatic Hyperplasia (BPH)

BPH — non-cancerous enlargement of the prostate — affects an estimated 50% of men by age 60 and up to 90% by age 85. It causes urinary symptoms including frequency, urgency, weak stream, and incomplete bladder emptying. Because DHT plays a role in prostate tissue growth, the concern that TRT might worsen BPH is legitimate and worth addressing directly.

The evidence here is more nuanced than the prostate cancer question, but broadly reassuring:

• Multiple studies show no significant worsening of urinary symptoms in men with mild-to-moderate BPH who begin TRT at physiological doses
• In men with severe, symptomatic BPH, TRT requires more careful monitoring and may not be appropriate without concurrent urological management
• The same Saturation Model applies DHT receptor saturation in prostate tissue means that TRT doses calibrated to restore normal ranges do not continuously stimulate further prostate growth

Men with known BPH should have a urological evaluation and baseline urinary symptom scoring before starting TRT. Ongoing monitoring ensures any changes are caught early. According to research indexed by the National Institutes of Health, men with hypogonadism and BPH can often be safely treated with testosterone therapy under appropriate monitoring protocols a finding that reflects how significantly clinical thinking has evolved.

Who Should Not Start TRT on Prostate Grounds

While the evidence has substantially reduced the prostate risk concern for most men, there are specific clinical scenarios where TRT is contraindicated or requires exceptional caution:

• Active, untreated prostate cancer: TRT is contraindicated. Androgen deprivation remains a treatment cornerstone for active disease, and adding exogenous testosterone is clinically unsound until the cancer is treated and stable.
• Elevated PSA without urological evaluation: A high baseline PSA should be evaluated before starting TRT — not as a reason to permanently withhold therapy, but to rule out active malignancy first.
• Recent prostate cancer treatment: Men who have completed treatment for localized prostate cancer and achieved remission may be candidates for TRT in select cases under specialist supervision. This is an evolving area the Prostate Cancer Foundation and urological societies are actively developing guidelines as evidence accumulates.
• Severe, uncontrolled BPH with significant urinary obstruction: Stabilize urological symptoms before adding TRT. For the vast majority of men with low testosterone and no active prostate disease, these contraindications do not apply.

The Bottom Line: What the Science Actually Tells Us

The fear that testosterone causes prostate cancer was never evidence-based. It was an inference drawn from research conducted on men with advanced metastatic cancer, extrapolated to healthy men, and allowed to calcify into clinical dogma without the large-scale trials needed to test it.

The Saturation Model explained the mechanism. The TRAVERSE trial confirmed the safety. The AUA updated its guidelines. And the epidemiological data — which consistently shows declining testosterone correlating with rising prostate cancer rates, not the reverse — has always pointed in the same direction.

None of this means TRT requires zero monitoring. PSA screening, urological evaluation when indicated, and regular labs are non-negotiable components of a responsible protocol. The benefits of TRT are significant but they are best captured inside a framework of clinical oversight, not outside it.

At TRTNYC, every patient receives comprehensive baseline testing — including PSA, digital rectal exam guidance, full hormone panel, and urological risk screening before treatment begins. We monitor prostate markers throughout your protocol and adjust accordingly. You get the benefits of optimized testosterone without uninformed risk. Book your consultation today and get a prostate safety evaluation built into your care plan from day one.

Frequently Asked Questions

Does TRT increase the risk of prostate cancer?

Current evidence — including the 2023 TRAVERSE trial, the largest RCT on testosterone therapy ever conducted — shows no statistically significant increase in prostate cancer risk in men on properly dosed TRT compared to placebo. The historical fear was based on inference, not direct proof.

Will my PSA go up if I start TRT?

A modest PSA increase of 0.3–0.5 ng/mL in the first 3–6 months is common and expected. This reflects normal prostate response to restored androgen levels, not cancer development. PSA typically stabilizes after the initial adjustment period.

Can I take TRT if I have BPH?

Men with mild-to-moderate BPH can often begin TRT with appropriate monitoring. Severe or symptomatic BPH may require urological management first. This is a clinical decision that should be made with your physician based on baseline symptom scoring and PSA evaluation.

Can I take TRT if I had prostate cancer?

In select men who have completed treatment for low-risk, localized prostate cancer and achieved remission, TRT may be considered under specialist supervision. This is an evolving area; consult both your urologist and TRT physician together.

How often should PSA be monitored on TRT?

At baseline before starting TRT, then at 3 and 6 months after initiation, and annually thereafter if results are stable. Any increase exceeding 1.4 ng/mL from baseline in the first year warrants urological evaluation.

Disclaimer: This article is written for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a licensed and qualified healthcare provider before making any decisions about hormone therapy or any other medical treatment. Individual results vary.