Question explored with the scientific record
Is testosterone replacement therapy for males safe?
The short version: for a man with confirmed hypogonadism, TRT's cardiovascular safety is unresolved, but the best recent trial found no excess in major cardiac events.
The TRAVERSE trial, the largest and most rigorous study to date, randomly assigned 5,246 high-risk men to testosterone gel or placebo and tracked them for a mean of 33 months. It found no significant difference in major adverse cardiac events: 7.0% in the TRT group versus 7.3% in the placebo group (hazard ratio 0.96, confidence interval 0.78–1.17) [8]. That is a clean result from a randomized, placebo-controlled trial with hard clinical endpoints. It is the strongest evidence we have.
But the picture is not settled. The Testosterone Trials, a smaller study in men aged 65 and older, found that TRT increased non-calcified coronary plaque volume over one year, even though no major cardiac events occurred in either group [8]. That is a surrogate endpoint—plaque volume is not a heart attack—but it is a signal that the long-term effect on arteries is not neutral. Meanwhile, a large Finnish registry study of 78,615 men found TRT users had a lower hazard for cardiovascular mortality (HR 0.80, CI 0.73–0.88) [4], and a separate analysis of 83,010 men found reduced risks of heart attack (HR 0.82), stroke (HR 0.70), and all-cause mortality (HR 0.53) [2]. These are observational, not randomized, and observational data can be confounded by the fact that healthier men are more likely to be prescribed TRT.
| Outcome | TRAVERSE (RCT, high-risk men) [8] | Finnish registry (observational) [4] | JAMA analysis (observational) [2] |
|---|---|---|---|
| Major cardiac events | 7.0% vs 7.3% (no difference) | — | — |
| Cardiovascular mortality | — | HR 0.80 (lower risk) | — |
| Heart attack | — | — | HR 0.82 (lower risk) |
| All-cause mortality | — | — | HR 0.53 (lower risk) |
On prostate safety, the evidence is more consistent. A meta-analysis found no significant increase in PSA levels with TRT, except a minimal rise with intramuscular formulations [6]. A retrospective study of 4 years of TRT found no increase in prostate cancer incidence beyond background rates [5]. The Finnish registry also found a lower hazard for prostate cancer (HR 0.80) [4], though that may reflect selection bias.
The main known risk is erythrocytosis—thickening of the blood—which guidelines flag by monitoring hematocrit and adjusting therapy if it exceeds 54% [7]. Fertility is suppressed by exogenous testosterone, which shuts down natural production; this is reversible in most men but can be permanent in some.
My call: for a man with confirmed symptomatic hypogonadism, TRT has a moderate net benefit for quality of life and metabolic parameters, with cardiovascular safety that appears neutral in the short-to-medium term based on the best trial, but with unresolved questions about long-term arterial effects. Confidence: moderate.
Sources examined 8
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Cardiovascular benefits and risks of testosterone replacement therapy in hypogonadal men with type 2 diabetes mellitus and/or the metabolic syndrome: a systematic review
A retrospective systematic review of testosterone replacement therapy (TRT) in hypogonadal men with type 2 diabetes mellitus and/or metabolic syndrome shows potential protective effects of TRT on all-cause mortality and major adverse cardiac events, but evidence is limited by he…
DOI: 10.15277/bjd.2018.192 -
Testosterone Replacement Therapy and Cardiovascular Risk—A Closer Look to Additional Parameters
The study discusses the implications of testosterone replacement therapy (TRT) on cardiovascular risk in older men, highlighting the need for further analysis on the normalization of testosterone levels and the impact of existing cardiovascular risk factors.
DOI: 10.1001/jamainternmed.2017.3890 -
Testosterone levels and type 2 diabetes in men: current knowledge and clinical implications
This narrative review reports that low testosterone and SHBG are associated with type 2 diabetes and cardiometabolic risk in men and that testosterone therapy has inconsistent metabolic benefits and unresolved cardiovascular safety concerns.
DOI: 10.2147/dmso.s50777 -
776 Prostate cancer incidence and cardiovascular mortality among users of testosterone replacement therapy in the Finnish Prostate Cancer Screening Trial
This study investigates the association between testosterone replacement therapy (TRT) and the risks of prostate cancer incidence and cardiovascular mortality among men aged 55-67 in the Finnish Prostate Cancer Screening Trial.
DOI: 10.1016/S1569-9056(16)60778-9 -
Prostate‐specific antigen changes and prostate cancer in hypogonadal men treated with testosterone replacement therapy
This study retrospectively reviews the effects of testosterone replacement therapy (TRT) on prostate-specific antigen (PSA) levels and the incidence of prostate cancer in hypogonadal men, finding that TRT effectively normalizes testosterone levels without significantly increasin…
DOI: 10.1111/j.1464-410x.2008.08240.x -
The Effect of Testosterone Replacement Therapy on Prostate-Specific Antigen (PSA) Levels in Men Being Treated for Hypogonadism
This systematic review and meta-analysis investigates the impact of testosterone replacement therapy on prostate-specific antigen (PSA) levels in men with hypogonadism, concluding that testosterone does not significantly increase PSA levels except when administered intramuscular…
DOI: 10.1097/MD.0000000000000410 -
Testosterone replacement therapy: For whom, when and how?
A comprehensive narrative review detailing the indications, formulations, monitoring, benefits, risks, and guideline context of testosterone replacement therapy (TRT) in men with hypogonadism, including late-onset hypogonadism, and discussing cardiovascular, metabolic, bone, sex…
DOI: 10.1016/j.metabol.2018.03.007 -
Cardiovascular Safety of Testosterone Replacement Therapy in Hypogonadal Men
An evidence-focused overview of the cardiovascular safety of testosterone replacement therapy (TRT) in hypogonadal men, highlighting that the TRAVERSE trial found no significant increase in major adverse cardiovascular events among high-risk men treated with testosterone, while …
DOI: 10.58931/cdet.2024.2330