For years, the question hung over every testosterone conversation: does TRT increase your risk of a heart attack or stroke? The TRAVERSE trial was designed to answer it. Here's what it found — and what it didn't.

The backstory

If you've ever looked into testosterone replacement therapy, you've probably hit a wall of conflicting information. Some studies suggested TRT increased cardiovascular risk. Others said it was protective. Most were too small, too short, or too poorly designed to settle the argument.

In 2015, the US FDA got fed up with the confusion and told testosterone manufacturers to fund a proper trial. The result was TRAVERSE — the largest randomised controlled trial ever conducted on TRT and heart risk. Published in the New England Journal of Medicine in 2023, it's now the single most important piece of evidence in this space. Healthy Male also published an article about this in September 2023, and the Androgen Society had a publication here

What they actually did

TRAVERSE enrolled over 5,200 men aged 45 to 80 across 316 sites in the United States. Every participant had confirmed low testosterone (two fasting morning levels below 10.4 nmol/L) plus symptoms of hypogonadism — things like low libido, fatigue, or reduced muscle mass.

Crucially, these weren't healthy blokes. Every man in the trial either already had cardiovascular disease or was at high risk of it. Think: existing heart disease, diabetes, high blood pressure, dyslipidaemia — often several of these stacked together. The researchers deliberately chose a high-risk population because if TRT was going to cause heart problems, this is where you'd see it.

Half received a daily testosterone gel. Half got a placebo. The primary question: did TRT cause more heart attacks, strokes, or cardiovascular deaths?

The headline result

No. TRT did not increase the rate of major adverse cardiovascular events (MACE) compared to placebo. The rates were essentially the same in both groups over a mean follow-up of about 22 months.

That's a meaningful finding. For men with confirmed low testosterone and symptoms, this trial provides genuine reassurance that appropriately prescribed TRT doesn't appear to trigger heart attacks or strokes — even in men who already have cardiovascular risk factors.

There was even a small, non-significant reduction in cardiovascular deaths in the testosterone group, though the trial wasn't powered to draw conclusions from that.

The bonus findings

TRAVERSE wasn't just about heart safety. Several secondary outcomes were noteworthy. There was a statistically significant

1) Diabetes Mellitus - possible reduction in diabetes progression in the testosterone group.

2) Anaemia (and fatigue) - About 16% of participants had anaemia at baseline, and TRT corrected it in a significantly greater proportion — 41% versus 28% on placebo at six months.

3) Sexual desire and frequency - Men on testosterone reported significant improvements in sexual desire and frequency, though not in erectile function, which makes sense in a population averaging 65 with extensive vascular disease where erection problems are more about blood vessel health than hormones.

4) Depressive symptoms - modest improvements to depressive symptoms

5) Prostate safety - no clear evidence of TRT increasing risk of high grade or any prostate cancer, although there is evidence of PSA rise compared to placebo.

What to watch

Not everything came back clean.

1) Non-fatal arrhythmias requiring intervention occurred in 5.2% of the testosterone group versus 3.3% on placebo, with atrial fibrillation more common in men receiving TRT.

2) There were more venous thromboembolic events — deep vein thrombosis and pulmonary embolism — in the testosterone group, which aligns with existing guidelines recommending caution in men with a history of clotting disorders.

3) Acute kidney injury was also slightly more common (2.3% vs 1.5%). These weren't the primary outcomes and the absolute numbers were small, but they're worth knowing about — especially if you have a personal or family history of blood clots or heart rhythm issues.

The fine print matters

Here's where intellectual honesty earns its keep. TRAVERSE answered the big question, but it has genuine limitations that a balanced reading demands.

The trial was cut short. It was originally designed for up to five years of follow-up with 6,000 participants. In practice, the mean treatment duration was about 22 months with 5,200 men enrolled. That's enough to assess short-to-medium-term safety, but we still don't have long-term data beyond a few years.

A lot of men stopped treatment. Over 60% of participants discontinued therapy during follow-up. When that many people drop out, it becomes harder to draw firm conclusions — particularly about what happens with sustained use.

Testosterone levels weren't pushed very high. Men started with a mean testosterone of about 7.9 nmol/L and increased by roughly 5 nmol/L at twelve months — hovering just above 12 nmol/L for much of the trial. That's low-normal at best. Some researchers have argued the study essentially tested modest testosterone replacement rather than full optimisation, which limits what we can say about higher-dose protocols.

The population was specific. These were older men (average age 63) with significant cardiovascular risk. The results apply most directly to that group. They don't automatically extend to younger men, men without cardiovascular risk factors, or men using injectable testosterone at different doses.

What this means for you

If you're an Australian or New Zealand bloke with confirmed low testosterone and your GP has discussed TRT with you, TRAVERSE provides the most robust reassurance we've ever had that it won't cause a heart attack or stroke when used appropriately.

But "appropriately" is doing a lot of work in that sentence. This trial supports TRT for men with:

  • Genuinely low testosterone confirmed on at least two fasting morning blood tests
  • Actual symptoms of hypogonadism — not just a number on a lab report
  • Proper medical supervision including regular blood monitoring (haematocrit, PSA, lipids)

It does not support testosterone use in men with normal levels chasing performance or anti-ageing benefits. As one of the trial's lead investigators put it: this trial should not be used as justification for widespread testosterone treatment in ageing men who haven't been properly assessed.

In Australia, testosterone is a Schedule 4 prescription medication regulated by the TGA, and PBS-subsidised access requires confirmed pathology and specific clinical criteria. In New Zealand, funded access through PHARMAC follows a similar evidence-based pathway. These aren't bureaucratic hurdles — they're guardrails that happen to align with exactly the kind of patient TRAVERSE studied.

The bottom line

TRAVERSE is a landmark trial. It tells us that for men with confirmed hypogonadism and cardiovascular risk, TRT doesn't increase the rate of heart attacks, strokes, or cardiovascular death — and may offer meaningful benefits for diabetes risk, anaemia, mood, and sexual wellbeing.

It also tells us to watch for arrhythmias and blood clots, that the long-term picture isn't fully drawn yet, and that this evidence applies to properly diagnosed men under medical supervision — not to anyone buying testosterone off the internet.

Good evidence doesn't remove the need for good clinical judgement. But it does make the conversation a lot clearer.

This article is general health information and does not replace individual medical advice. If you're considering TRT, talk to your GP about whether it's appropriate for your specific situation.