TRT and the Prostate: What Your PSA Really Tells You

There is one question that comes up in nearly every first consultation, usually near the end and phrased as an afterthought: "And the prostate? Won't this give me cancer?" Often there is a father or a father-in-law behind it who was diagnosed with prostate cancer, and the concern is anything but unreasonable.

It is, however, now well studied. Since 2023 there has been a randomised trial covering more than five thousand men, and the answer is more reassuring than the reputation of the therapy suggests. Reassuring does not mean unconditional, though, and the conditions are what this article is really about.

Where the fear comes from

The origin lies in 1941. Charles Huggins showed that withdrawing testosterone makes prostate tumours shrink, a discovery that still shapes the treatment of advanced prostate cancer today. From it came the reverse inference: if withdrawal helps, supply must harm.

That inference is logically tempting and biologically wrong. It assumes the prostate responds evenly to androgens across the whole concentration range. It does not. How this way of thinking survived for decades is covered in the wider context in TRT safety.

The saturation model, and the objections to it

The explanation is the saturation model. Prostate tissue is extremely sensitive to androgens at very low concentrations but becomes insensitive to further increases above a certain point. The reason is androgen receptor binding: it is already maximal at testosterone concentrations well below the normal physiological range. Additional testosterone finds no free binding sites and correspondingly does little to the prostate [3].

The model explains why castration reduces tumour burden while replacing a deficiency up into the normal range changes little in the tissue. It is the mainstream explanation today, and it fits the clinical data.

In fairness, it has been challenged. A critical appraisal of the original publication concludes that parts of the evidence cited at the time were taken out of context and applied too freely to prostate cancer, and advises caution when extending the model to cancer patients [6]. That does not undo the clinical safety data, but it is a good reason to lean on trial results rather than on an explanatory model.

What the randomised data show

The most robust answer comes from the prostate safety analysis of the TRAVERSE trial. It enrolled 5,246 men aged 45 to 80 with two testosterone measurements below 300 ng/dL, hypogonadal symptoms and cardiovascular risk, randomised to testosterone gel or placebo. A total of 5,204 men were analysed across 14,304 person-years [1].

For the primary endpoint the hazard ratio was 1.62 with a confidence interval running from 0.39 to 6.77. That wide interval is the honest reading: with eight events across both groups combined, a small residual risk cannot be excluded, but a large one can. No signal, and no blanket reassurance either [1].

The second pillar is a meta-analysis that treats endogenous and administered testosterone separately. Across 20 estimates from prospective cohorts, a 5 nmol/L rise in the body's own testosterone gave a relative prostate cancer risk of 0.99, meaning precisely no association, and with no heterogeneity between studies. Across eleven treatment trials, prostate cancer as an adverse event carried a relative risk of 0.87 [2].

Why PSA rises slightly on therapy

A man with testosterone deficiency has an under-stimulated prostate. Once replacement begins, the tissue resumes normal activity and PSA rises modestly. In TRAVERSE it rose more in the testosterone group than on placebo [1]; in the meta-analysis the mean difference was 0.10 ng/mL [2].

That is the order of magnitude at stake: a tenth of a nanogram, not a doubling. Going from 0.8 to 1.1 ng/mL in the first year of therapy is not a warning sign. It is the expected behaviour of an organ that is being properly supplied again.

Which rise gets investigated

What counts is not the absolute figure alone but the speed of change. Two markers are in common use [4]:

• A rise of more than 1.4 ng/mL within twelve months — urological referral, regardless of the starting value.
• An absolute value above 4 ng/mL — investigation, and from 3 ng/mL in men at elevated risk.

Add to that any palpable abnormality or firm area on examination, which always warrants investigation irrespective of the laboratory number.

Before drawing conclusions from a single result, look at the conditions it was measured under. PSA reacts sensitively to mechanical stimulation and inflammation: ejaculation within the preceding 48 hours, a rectal examination shortly before the blood draw, and above all prostatitis can push it up, the last of these by a multiple. For the frequently cited long bike ride the data are contradictory and a large effect is unlikely. An abnormal value under those circumstances should be repeated, not biopsied straight away. The full monitoring picture is set out in TRT blood work.

What has to be settled before starting

This is the most important limitation of the good data, and it is rarely mentioned. TRAVERSE excluded men with a PSA above 3.0 ng/mL and men with severe urinary symptoms from the outset [1]. The trial therefore shows that therapy is safe in carefully preselected men. It says nothing about the man with a PSA of 5.2 ng/mL.

In practice: a PSA measurement before the start, a history including family burden, and where anything is abnormal, urological assessment before therapy rather than alongside it. Known, untreated prostate cancer is a contraindication. An unclear PSA is not an exclusion but an instruction to clarify.

Monitoring afterwards follows the usual rhythm: shorter intervals in the first year, six-monthly once the picture is stable, together with testosterone, estradiol and hematocrit.

After treated prostate cancer

This group deserves its own answer, because it is affected particularly often: men who have had surgery or radiotherapy frequently report exactly the symptoms that point to testosterone deficiency.

A systematic review pooled 13 studies spanning twenty years, covering 109 men after curative treatment of high-risk prostate cancer. The rate of biochemical recurrence was 0.00, below what would be expected in this group anyway. The authors stress in the same breath that the evidence is of very low quality and that therapy remains investigational in this situation [5].

That is how it has to be put: there are indications that it can work, but no certainty. Anyone considering testosterone therapy after treated prostate cancer needs their urologist's agreement and co-management, not a remote diagnosis.

And the matter of urination

The second concern, voiced less often: does the prostate grow on testosterone, and does passing urine get harder? Here too TRAVERSE gives a clear answer. The standardised symptom score did not differ between groups, and acute urinary retention, biopsies, operations and newly prescribed medication for bladder symptoms were no more frequent [1].

For the large majority of patients that means therapy does not worsen bladder function. Men who already have pronounced symptoms should be assessed urologically first, because they were the ones excluded from the trial.

If you are unsure whether your symptoms fit testosterone deficiency, the online self-test gives a first indication. Interpreting a PSA result belongs in a conversation, and that can be arranged by telemedicine.

FAQ

Does TRT increase the risk of prostate cancer?

On the current evidence, no. In the randomised prostate safety analysis of 5,204 men, high-grade cancers occurred in 0.19 percent on testosterone and 0.12 percent on placebo, with no significant difference [1]. A meta-analysis additionally found no association between a man's own testosterone level and prostate cancer risk [2].

My PSA went from 0.9 to 1.3 on TRT. Is that bad?

No, that sits within the expected range. The average rise on therapy is around 0.10 ng/mL [2], and a deficiency state before treatment suppresses the value artificially. It becomes a matter for investigation above a rise of 1.4 ng/mL within a year or an absolute value above 4 ng/mL [4].

Do I need to see a urologist before starting?

Not necessarily, but a PSA result and a proper history belong before the start. If PSA is above 3 ng/mL, if there is a palpable abnormality, or if there is a family history, then yes: those men were excluded from the safety trials, and the good numbers do not automatically apply to them [1].

I had prostate cancer and was operated on. Is TRT an option?

Possibly, but only in agreement with your urologist. The available data from 13 studies covering 109 high-risk patients show no increased recurrence rate, but the evidence is of very low quality, which is why therapy in this situation is considered investigational [5].

Does the prostate grow on testosterone?

Not to a clinically relevant degree. Urinary symptoms did not increase in the large randomised trial, and retention, procedures and new bladder medication were no more common than on placebo [1]. Where pronounced symptoms already exist, the prostate should be assessed beforehand.

Further Reading

• TRT safety: myths and facts checked
• Hematocrit and TRT: when the number matters
• TRT blood work: which values are monitored