The headline answer
Restoring low testosterone to the normal range has not been shown to cause prostate cancer. That conclusion reverses a belief that shaped medicine for decades, and the reversal has a clear logic: prostate tissue is very sensitive to testosterone at very low levels, then stops responding once its receptors are full. Researchers call this the saturation model.
That is not the same as saying testosterone is irrelevant to the prostate. Testosterone can still feed a cancer that already exists, especially one that has been suppressed with hormone therapy, and long-term safety beyond a few years is not settled. That is why PSA is checked before and during treatment, and why men with prostate cancer are handled differently.
Where the fear started: Huggins and Hodges, 1941
In 1941, Charles Huggins and Clarence Hodges reported that castration or estrogen lowered a blood marker of prostate cancer activity in men with metastatic disease, while androgen injections pushed it up. The finding launched hormone therapy for advanced prostate cancer, which still saves lives today.
The lesson most doctors took from it was broader: if lowering testosterone shrinks prostate cancer, raising testosterone must grow it. For decades that idea discouraged testosterone treatment in older men, even though the original data came from a small number of men with widespread cancer whose testosterone had been driven to near zero. The question nobody tested for decades was what happens when testosterone moves from low to normal in men without known cancer.
The saturation model, explained
In 2009, Abraham Morgentaler and Abdulmaged Traish pulled together studies from 1941 onward and proposed the saturation model. Their review found that prostate growth is exquisitely sensitive to changes in androgen at very low concentrations but becomes insensitive at higher levels. The reason is the androgen receptor: maximal binding is reached at serum testosterone concentrations well below the normal adult range.
Think of it the way a sponge holds water. A dry sponge soaks up every drop, but once it is full, pouring more water on it changes nothing. The table shows how that plays out.
| Testosterone situation | Effect on prostate tissue |
|---|---|
| Castrate or near-castrate levels | Highly sensitive: lowering testosterone shrinks cancer, raising it can fuel growth |
| Low to normal adult range | Receptors close to full: further increases produce little additional effect |
| Testosterone added after hormone therapy for cancer | Behaves like the first row, which is why this group needs specialist care |
The model accounts for both observations: the dramatic effect of castration Huggins saw, and the small effect of testosterone therapy in men who are not castrated.
What the TRAVERSE prostate data added
A model is only as good as its test, and the strongest test so far came from the TRAVERSE trial. Its prostate safety analysis followed 5,204 men aged 45 to 80 with low testosterone and symptoms who were randomized to testosterone gel or placebo for a mean of about 22 months of treatment.
- High-grade prostate cancer: 5 of 2,596 men on testosterone (0.19%) and 3 of 2,602 on placebo (0.12%), a difference that was not statistically significant.
- Any prostate cancer, acute urinary retention, prostate procedures, biopsies and new medicines for urinary symptoms: no significant differences.
- Urinary symptom scores: no difference between groups.
- PSA: rose more in the testosterone group than with placebo.
Two cautions keep these numbers honest. Men with a PSA above 3.0 ng/mL or severe urinary symptoms were excluded, so the trial describes carefully screened men. And the follow-up was a few years, which is short for a disease that usually grows slowly. The Endocrine Society’s 2026 statement says long-term safety, including for prostate cancer, has not been established.
Why PSA is still checked before and during TRT
PSA is a protein made by the prostate, and MedlinePlus explains that raised levels can come from cancer but also from benign enlargement, inflammation and other causes. On testosterone therapy it serves two purposes: it screens for a cancer that was already there before treatment, and it shows whether the prostate is reacting more than expected once treatment starts.
The AUA guideline asks clinicians to measure PSA in men over 40 before starting testosterone, to exclude a prostate cancer diagnosis. The same guideline tells clinicians to inform patients that evidence does not link testosterone therapy to developing prostate cancer, and that for men with a history of prostate cancer the evidence is too thin to quantify risk and benefit.
In practice that means a baseline PSA, repeat checks in the first months of treatment and then on a regular schedule, and a clear plan for what counts as a meaningful rise. Our pages on a rising PSA on TRT and a high PSA before TRT explain how those results are handled. Men with a family history of prostate cancer start that conversation with extra context.
Who needs a different conversation
The saturation model is reassuring for men with low testosterone and a healthy prostate. It says much less about men who already have prostate cancer, or who might. Testosterone labels list known or suspected prostate cancer as a reason not to use the drug, and that line has not moved.
A few situations call for a slower, more specialized path:
- A PSA that is already high or rising before any treatment. The first job is to find out why.
- An abnormal prostate exam or urinary symptoms that have changed quickly.
- Prostate cancer treated with surgery or radiation. Some urologists do consider testosterone in selected men after curative treatment, but the decision belongs with the cancer team.
- Prostate cancer on active surveillance or hormone therapy. This is the group closest to the steep part of the saturation curve.
None of these mean a man’s symptoms do not matter. They mean the risk side of the decision needs more information than a single clinic visit can provide.
How Ultimate Male screens the prostate before TRT
At our San Gabriel and Downey clinics, the TRT pre-screening panel includes PSA alongside total testosterone, estradiol and a complete blood count, drawn on site with results in 24 to 48 hours. Your PA-C or MD reviews the PSA in light of your age, prior results and urinary symptoms before any treatment decision, and repeats it during follow-up.
If your PSA is borderline or climbing, the next step is a closer look, not a quick start, and referral to a urologist when the picture calls for it. Men who have been treated for prostate cancer can read our page for men after prostate cancer treatment. For everyone else, the testosterone therapy overview covers what monitoring looks like once treatment begins, and the TRAVERSE heart findings are covered in our article on testosterone and heart safety.
