Testosterone Replacement Therapy and the Heart: A Decade of Alarm, a Meta-Analysis of 9,000 Men - and the One Signal That Survived
Updated: 4 days ago
For most of the last decade, testosterone replacement carried a shadow. Observational studies in 2013 and 2014 linked it to heart attacks, strokes and death, regulators added warnings, and men with genuinely low testosterone were left weighing symptom relief against a risk nobody could quantify. Randomised evidence has since arrived in volume, and the picture it paints is calmer - but not entirely clear. Major cardiovascular events do not rise. Heart rhythm disturbances do. Understanding both halves of that finding is what separates an informed decision from a headline.
The evidence
The evidence comes from the StatPearls chapter on the physiology of testosterone (updated 2026) and a 2025 systematic review and meta-analysis of long-term cardiovascular outcomes across 23 randomised trials and 9,280 men, published in the American Journal of Cardiovascular Drugs (Braga and colleagues 2025); the 2023 TRAVERSE trial is referenced as described within that meta-analysis. This article is general education about a prescribed hormone therapy, not medical advice; testosterone is a controlled prescription medicine, and its use is a decision for a clinician based on confirmed deficiency.
What happened
What testosterone therapy is for, and what it costs. Indications include primary hypogonadism from testicular failure and hypogonadotropic hypogonadism from pituitary or hypothalamic dysfunction, alongside delayed puberty under supervision and gender-affirming therapy. Treatment requires regular monitoring of androgen levels, prostate-specific antigen, haemoglobin and haematocrit. Adverse effects include erythrocytosis, infertility from suppression of luteinising hormone and FSH with reduced testicular size, acne, accelerated male-pattern baldness, gynaecomastia through aromatisation to oestradiol, prostate enlargement, mood and behavioural disturbance, and rarely hepatic adenomas and cholestatic jaundice (StatPearls 2026).
The observational scare was not confirmed by trials. Earlier observational studies, notably a 2013 analysis, associated testosterone with myocardial infarction, stroke and mortality - findings not borne out by subsequent randomised evidence (Braga and colleagues 2025).
No excess of major events; more arrhythmias. Pooling 23 randomised trials in 9,280 middle-aged and older men, testosterone therapy showed no significant difference from placebo in all-cause mortality, myocardial infarction or stroke, but a significantly increased risk of cardiac arrhythmias (relative risk 1.53, 95 percent confidence interval 1.20-1.97); the authors conclude therapy appears generally safe for major cardiovascular events but that the arrhythmia signal warrants clinical monitoring, consistent with the direction of the large 2023 TRAVERSE trial (Braga and colleagues 2025).
The current answer
The cardiovascular question about testosterone therapy now has a reasonably settled answer with one important footnote. When men with confirmed low testosterone are randomised to replacement or placebo and followed for years, they do not die more, have more heart attacks, or have more strokes - the randomised evidence, pooled across more than nine thousand men and echoed by the largest dedicated safety trial, does not reproduce the alarming associations that came out of retrospective database studies a decade ago. Those earlier signals are best understood as the product of who was being prescribed testosterone and why, rather than of the hormone itself.
The footnote is rhythm. Across the trials, men on testosterone had roughly half again the rate of cardiac arrhythmias, most relevantly atrial fibrillation, and that is a real effect with a plausible mechanism - testosterone thickens the blood by driving red-cell production, shifts fluid, and acts on cardiac tissue - and it means that treatment is not risk-free, particularly for older men or those with existing heart disease. The rest of the ledger is the familiar list of a potent hormone: the blood count rises and must be watched, sperm production and testicular size fall because the brain stops signalling the testes, the prostate is monitored, and skin, hair and mood can all change. The right framing, then, is not "testosterone is dangerous to the heart" nor "testosterone is safe" but "testosterone replacement, given to men who genuinely need it and monitored properly, does not appear to increase major cardiovascular events, and does increase arrhythmia risk enough to justify surveillance."
Two things follow. The first is that the case for therapy rests on a confirmed deficiency with symptoms - the reassuring safety data come from men who had low testosterone, not from men using it for performance or vanity, where the risk-benefit balance is entirely different. The second is that monitoring is not bureaucracy: the haematocrit, the PSA and the heart rhythm are exactly where the known harms show up first.
How certain is this?
Certainty is high that testosterone therapy in hypogonadal men does not increase major adverse cardiovascular events or mortality in randomised trials, and high that it increases the risk of cardiac arrhythmia. Certainty is moderate on the absolute size of the arrhythmia risk in different age and risk groups, and on longer-term outcomes beyond the trial follow-up periods. Who this covers: men with clinically confirmed hypogonadism considering or receiving prescribed testosterone; it does not cover supraphysiological or non-prescribed use, or any individual's decision. What would change our mind: extended follow-up of the large trials, or data clarifying which men carry the arrhythmia risk.
The randomised trials cleared testosterone of the heart attacks and strokes the databases had pinned on it - and convicted it of arrhythmia instead. Treat a confirmed deficiency, monitor the blood and the rhythm, and understand that none of this safety data applies to using it without one.
What this means in practice
Understand that in men with confirmed low testosterone, prescribed replacement does not appear to raise heart attacks, strokes or mortality in randomised trials.
Take the arrhythmia signal seriously: roughly a 50 percent relative increase, most relevantly atrial fibrillation - report palpitations or an irregular pulse promptly, especially if older or with heart disease.
Expect and accept monitoring - haematocrit, PSA and rhythm - as the mechanism by which the known harms are caught early.
Know the trade-offs beyond the heart: suppressed fertility and testicular size, thicker blood, and possible prostate, skin, hair and mood changes.
Recognise that the safety data come from men who needed the hormone; they do not apply to performance or non-prescribed use, where the risk-benefit balance is different.
Never start, stop or adjust testosterone on your own; it is a controlled prescription decided on confirmed deficiency by a clinician.
Ohana Performance Institute does not give pharmacological advice; questions about hormones and medication belong with a clinician. For the evidence behind this article and hundreds more, explore the full research library.
References
Physiology, testosterone. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated 2026. https://www.ncbi.nlm.nih.gov/books/NBK526128/
Last reviewed: 3 September 2026. Re-review on the next major testosterone safety trial or guideline, or by September 2028.
Educational content, not medical advice. Legality varies by country — check your local laws.
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