Testosterone and the heart: the fear of an enlarged heart, coagulation, and what the evidence allows
The fear that testosterone replacement enlarges the heart or causes a heart attack comes from anabolic abuse and from a scientific scare that did not hold up. At the physiological dose, with monitoring, testosterone does not do what the patient fears. A sober, favorable and honest guide, between poison and miracle.
The patient's fear: does testosterone enlarge the heart or cause a heart attack?
The right question is not whether testosterone touches the heart, but at what dose and in what context.
It is a common and legitimate worry in the office: will replacing testosterone enlarge the heart, thicken the cardiac muscle, or trigger a heart attack. The fear comes from two sources that blur together, the image of the bodybuilder who abuses steroids and a scientific scare from a decade ago that made headlines. It is worth separating the two, because the answer changes completely with the dose.
The thesis here is sober and favorable to testosterone, without becoming advertising: at the physiological replacement dose, with indication and monitoring, testosterone does not do what the patient fears. It is not the fountain of youth the market sells, but it is also not the cardiac poison the headline suggested. What the evidence allows is a position in the middle, and it is reassuring.
The enlarged heart is a phenomenon of abuse, not of replacement
Pathological cardiac hypertrophy appears with abuse doses, not with monitored physiological replacement.
The fear of the enlarged heart has a real address, and it is not replacement. It lives in the abuse of androgenic steroids at supraphysiological doses. In the HAARLEM study, men who used abuse doses developed left ventricular hypertrophy and cardiac dysfunction on echocardiography, with partial regression after they stopped (Smit et al., HAARLEM, 2021). In other words, the heart thickens when the dose is the gym dose, often multiples of the physiological, and not when it is the replacement dose.
Physiological replacement is another story. Its goal is to return testosterone to the normal adult range, not to exceed it. In that range, with follow-up, the pathological hypertrophy the patient fears is not the expected finding. The right conversation separates the high-dose pellet and the anabolic cycle, which do remodel the heart, from indicated and dosed replacement, which does not. The villain is the excess, not the hormone.
The harm scare and why it did not hold up
Two observational studies scared the field; the higher-quality evidence that came later did not confirm the harm.
The second source of fear is historical. In 2013 and 2014, two observational studies suggested more cardiovascular events with testosterone and triggered a regulatory warning and a wave of headlines. They were heavily criticized for methodological problems, including how the outcomes were counted and how the groups were compared, to the point that medical societies asked for a public correction.
What resolved the question was not rhetoric, it was the higher-quality evidence that came afterward. Large individual-participant meta-analyses and, above all, a randomized trial designed for cardiovascular safety did not confirm the harm (Yeap et al., 2024, TRAVERSE, 2023). Testosterone was indeed unfairly demonized by that batch of fragile studies. Acknowledging that is fair. The next step is not to swap one exaggeration for another.
TRAVERSE: the trial that settled safety
The definitive trial shows safety in major events, not superiority; and it carries a signal that deserves respect.
TRAVERSE is the trial that was missing: over five thousand hypogonadal men at high cardiovascular risk, randomized to testosterone or placebo, with a major cardiac endpoint as the target. The result was non-inferiority, testosterone did not increase heart attack, stroke and cardiovascular death compared to placebo (TRAVERSE, 2023). That is safety, and it is the direct answer to the fear of a heart attack: in the largest test done, there was no feared harm.
Two honest caveats, which strengthen the message rather than weaken it. First, non-inferiority is safety, not superiority; the trial does not prove testosterone protects the heart, only that it does not attack it. Second, the testosterone arm had more atrial fibrillation and more pulmonary embolism (TRAVERSE, 2023). These signals do not cancel the overall safety, but they call for selection and follow-up, and they connect to the next point.
Low testosterone is a risk marker, and that matters
The man with very low testosterone dies more, but the number is a marker of health, not an isolated trigger.
There is a point in favor of testosterone that the evidence supports well: the man with very low endogenous testosterone has, on average, higher all-cause and cardiovascular mortality. The individual-participant meta-analysis showed this association consistently (Yeap et al., 2024). It makes clinical sense, and it helps explain why deficiency is not a cosmetic detail.
The precise reading is the one that supports the conduct. This is an association, and low testosterone works largely as a marker of poor health, the sick body drives testosterone down, and not only the other way around. That is why the finding does not become, by itself, a prescription to replace in everyone. It says real deficiency deserves attention, not that optimizing the number protects the heart of someone already healthy.
The real and manageable risk: hematocrit and coagulation
Coagulation was not dismissed; it is a real, early and, above all, monitorable risk.
Here is the part that deserves honesty, not bravado. The most consistent laboratory effect of testosterone is the rise in hematocrit, erythrocytosis, which thickens the blood. And the thrombotic risk is not dismissed: testosterone therapy was associated with more venous thromboembolism, especially in the first six months, in men with and without hypogonadism (Walker et al., 2020), which dialogues with the pulmonary embolism seen in TRAVERSE (TRAVERSE, 2023).
The point that closes in favor of practice, however, is that this risk is manageable, and it is exactly what good conduct does. Guidelines require confirming the diagnosis, using a physiological dose and monitoring hematocrit, holding or adjusting above 54 percent (Bhasin et al., 2018). Put directly to the patient: the risk of a clot exists, it is greater at the start, and that is precisely why the blood test is followed. Saying it does not exist would be weaker, and less true, than saying it is controlled.
| Dimension | Physiological replacement (indicated) | Supraphysiological abuse |
|---|---|---|
| Dose goal | Normal adult range | Multiples of the normal range |
| Effect on the heart | No pathological hypertrophy expected | Hypertrophy and dysfunction (HAARLEM) |
| Major events | Non-inferiority in TRAVERSE | Context of cardiovascular risk |
| Follow-up | Hematocrit and clinic monitored | No medical monitoring |
Synthesis: safe when indicated and monitored
Neither poison nor fountain of youth. Indication and monitoring do the work.
Putting it together, the message is favorable and defensible. Testosterone was unfairly demonized by fragile studies, the enlarged heart is a phenomenon of abuse and not of replacement (Smit et al., 2021), and the largest safety trial did not find the feared cardiac harm (TRAVERSE, 2023). To the patient who fears the enlarged heart, the honest answer is reassuring: at the replacement dose, with follow-up, that is not what happens.
The same honesty that dispels the exaggerated fear also restrains the exaggerated enthusiasm. TRAVERSE safety is non-inferiority, not proof of protection; low testosterone is a risk marker, not an isolated trigger (Yeap et al., 2024); and coagulation is a real, early and monitorable risk (Walker et al., 2020). The position that holds before any colleague is simple: testosterone replacement is safe when it is truly indicated, dosed in the physiological range and monitored, above all the hematocrit (Bhasin et al., 2018). It is not poison, and it is not a miracle.
| The evidence supports | The evidence does not authorize |
|---|---|
| Physiological replacement does not cause the pathological enlargement of the heart | Treating testosterone as proven cardioprotective |
| Safety in major events in TRAVERSE (non-inferiority) | Saying the clot risk has been dismissed |
| Very low testosterone is associated with higher mortality | Replacing in a healthy man to optimize the number |
| The thrombotic risk is manageable with monitoring | Skipping hematocrit follow-up |
Why this matters for your care
This article answers a frequent office question, the fear that replacing testosterone enlarges the heart or causes a heart attack, resting only on indexed primary sources: the TRAVERSE trial, the individual-participant meta-analysis by Yeap et al., the HAARLEM study on abuse, the study by Walker et al. on thromboembolism, and the Endocrine Society guideline. Testosterone replacement is a matter of medical prescription and follow-up; there is no dosing recommendation here. Educational content; it does not replace an individual evaluation and does not constitute a prescription. The Research Notes gather the other pieces.
References
- Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy (TRAVERSE). New England Journal of Medicine. 2023. doi:10.1056/NEJMoa2215025
- Yeap BB, Marriott RJ, Dwivedi G, et al. Associations of Testosterone and Related Hormones With All-Cause and Cardiovascular Mortality and Incident Cardiovascular Disease in Men: Individual Participant Data Meta-analyses. Annals of Internal Medicine. 2024. doi:10.7326/M23-2781
- Smit DL, Buijs MM, de Hon O, et al. (HAARLEM). Anabolic Androgenic Steroids Induce Reversible Left Ventricular Hypertrophy and Cardiac Dysfunction: Echocardiography Results of the HAARLEM Study. Frontiers in Reproductive Health. 2021. doi:10.3389/frph.2021.732318
- Walker RF, Zakai NA, MacLehose RF, et al. Association of Testosterone Therapy With Risk of Venous Thromboembolism Among Men With and Without Hypogonadism. JAMA Internal Medicine. 2020. doi:10.1001/jamainternmed.2019.5135
- Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism. 2018. doi:10.1210/jc.2018-00229
Educational and scientific content. It does not constitute diagnosis, prescription or individual clinical guidance, and does not replace a medical consultation. Management decisions must be individualized by a physician.