TRT and Heart Health: What the TRAVERSE Trial Actually Found (2026 Evidence Review)

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The Most Googled TRT Fear Has a Real Answer Now

If you've spent any time researching testosterone replacement therapy, you've run into the cardiovascular question. Maybe your doctor flagged it. Maybe you read an article warning about heart attacks. Maybe someone in a forum told you TRAVERSE proved TRT was safe, and someone else told you that was spin.

The anxiety is understandable. For a decade, the regulatory and media messaging around TRT and heart health was genuinely confusing — conflicting studies, an FDA label update in 2015, and clinic marketing that either catastrophized the risk or dismissed it entirely.

The TRAVERSE trial, published in 2023, is the closest thing to a definitive answer the field has ever produced. It was the largest randomized controlled trial of testosterone therapy ever conducted — over 5,000 men, nearly three and a half years of follow-up, funded by an independent NIH-sponsored research consortium.

Here's what it actually found — and just as importantly, what it didn't study, and what the findings don't cover.

Why the Cardiovascular Concern Existed in the First Place

Two observational studies in 2013 and 2014 set off the alarm.

The Vigen et al. study (JAMA, 2013) reported higher rates of death, heart attack, and stroke in men who received TRT after coronary angiography. The study had significant methodological problems — including a calculation error that had to be corrected — but the FDA acted on it. The 2015 FDA label change required all testosterone products to carry a warning about potential cardiovascular risk.

The Finkle et al. study (PLOS ONE, 2014) found elevated heart attack risk in older men in the 90 days after starting TRT. Again, observational design, no randomization, confounding factors (sicker men are more likely to get TRT AND more likely to have cardiac events) — but the finding added to the concern.

The Basaria et al. 2010 trial (Testosterone in Older Men with Mobility Limitations) was stopped early after an imbalance in cardiovascular adverse events in the testosterone arm — though the trial was small (106 men) and enrolled a particularly frail, high-risk population.

These studies were legitimate signals. They were not proof of causation. And they were in very high-risk patient populations, not the typical 40-year-old who's been told his testosterone is low.

The TRAVERSE Trial: What It Was Designed to Answer

The TRAVERSE (Testosterone Replacement Therapy for Assessment of Long-term Vascular Events and Efficacy ResponSE in Hypogonadal Men) trial was specifically designed to answer the cardiovascular safety question that the observational studies left open.

Design:

• Randomized, double-blind, placebo-controlled — the gold standard
• 5,246 men enrolled across 316 sites in the US
• All enrolled men had confirmed hypogonadism (baseline total T below 300 ng/dL on two morning measurements)
• Critical enrollment criterion: All participants had pre-existing cardiovascular disease OR were at high risk for cardiovascular disease (elevated Framingham risk score)
• Intervention: testosterone undecanoate (a long-acting injectable) vs. placebo
• Median follow-up: 33 months (~2.75 years); some participants followed for up to 5 years

Primary endpoint: Major adverse cardiovascular events (MACE) — the composite of cardiovascular death, non-fatal heart attack, and non-fatal stroke

Published: New England Journal of Medicine, July 2023

What TRAVERSE Found — The Full Picture

Primary Endpoint: No Increased Risk of Heart Attack or Stroke

The headline finding: TRT was non-inferior to placebo for MACE.

The differences are not statistically significant. In a high-risk cohort followed for nearly three years, testosterone replacement did not increase the rate of heart attacks, strokes, or cardiovascular death compared to placebo.

This directly refutes the 2013–2015 observational signal.

Secondary Findings: Two Real Signals Require Attention

TRAVERSE found two secondary endpoints that were significantly higher in the testosterone arm:

1. Atrial Fibrillation (AFib)

• TRT group: 3.5%
• Placebo group: 2.4%
• Absolute risk increase: approximately 1.1 percentage points
• Odds ratio: approximately 1.57 (statistically significant)

AFib is an irregular heart rhythm that increases stroke risk and can cause symptoms including palpitations, fatigue, and shortness of breath. The mechanism by which TRT may increase AFib risk is not fully established — proposed pathways include T-induced left ventricular hypertrophy, electrolyte changes via androgen-driven aldosterone activity, and direct effects on cardiac electrical conduction. It's worth noting that most AFib cases in both arms were detected incidentally on ECG or monitoring, not as acute symptomatic events.

2. Pulmonary Embolism (PE)

• TRT group: 0.9%
• Placebo group: 0.5%
• Absolute risk increase: approximately 0.4 percentage points
• Odds ratio: approximately 1.71 (statistically significant)

PE risk is mechanistically linked to erythrocytosis — the most well-understood cardiovascular risk factor on TRT. Testosterone stimulates erythropoietin production, which raises red cell mass and hematocrit. Above roughly 52–54%, blood viscosity increases meaningfully, elevating clot risk including DVT and PE. This is the same mechanism that makes hematocrit monitoring non-optional for men on TRT.

What TRAVERSE Did Not Find

No significant differences were observed for:

• All-cause mortality
• Deep vein thrombosis (DVT) — though a non-significant trend in the direction of more DVT in the TRT arm
• Peripheral artery events
• Revascularization procedures

The Critical Context: Who Was in This Trial

The TRAVERSE population is not the average TRT candidate.

Every participant had pre-existing cardiovascular disease (prior MI, stroke, coronary artery disease, peripheral vascular disease) or high cardiovascular risk (defined by Framingham risk score plus at least one risk factor: hypertension, dyslipidemia, smoking, diabetes, obesity).

The average participant was 63 years old, obese (mean BMI ~35), and had multiple cardiometabolic risk factors.

This is an important limitation to understand clearly: TRAVERSE tells us a great deal about TRT safety in older, sicker men who already have cardiovascular disease. It tells us relatively little about a 42-year-old with documented hypogonadism, no prior cardiac events, and normal lipids and blood pressure who would be a routine TRT candidate.

For typical lower-risk TRT candidates, the TRAVERSE data provides reassurance, not a clean safety bill. The AFib and PE signals were found in a high-risk group. Whether those signals are smaller, equivalent, or absent in lower-risk men is not answered by TRAVERSE.

The testosterone field's consensus post-TRAVERSE: for men without prior cardiac events, the evidence for harm is weak and the evidence for non-inferior primary outcomes in high-risk populations is now strong. For men with recent acute cardiac events, caution and specialist input remain appropriate.

What TRT Actually Does to Cardiovascular Risk Factors

Understanding the direct effects on individual risk factors helps build a more complete picture than trial headlines alone.

Hematocrit / Erythrocytosis

This is the most significant and most modifiable cardiovascular risk factor on TRT.

Hematocrit typically peaks at 3–6 months after starting TRT and then stabilizes. Men with obstructive sleep apnea carry additional risk because untreated apnea independently drives erythrocytosis via hypoxia — stacking with TRT-driven EPO stimulation.

Lipids

TRT's effect on lipid panels is modest and depends heavily on baseline status, dose, and delivery method.

• HDL (good cholesterol): TRT typically reduces HDL by 4–8%. This is more pronounced with oral/buccal testosterone and at supraphysiologic doses. Subcutaneous or lower-dose protocols show smaller HDL reduction.
• LDL: Generally neutral to modestly reduced, especially in men with metabolic syndrome where TRT-driven improvement in insulin sensitivity contributes.
• Triglycerides: Often decreased in men with metabolic syndrome — a favorable effect related to improved insulin sensitivity and body composition.
• Total cholesterol: Minor effects; not typically a clinical concern.

The net lipid effect of TRT in men with metabolic syndrome is generally favorable or neutral. In metabolically healthy men with normal lipids, a modest HDL reduction is possible and worth monitoring.

Blood Pressure

TRT does not significantly raise blood pressure in most men at standard therapeutic doses. Minor fluid retention in early months (from estradiol-driven sodium retention via aldosterone) can cause a transient 1–3 mmHg systolic increase that typically resolves. Men with pre-existing hypertension should monitor BP at their standard frequency.

Insulin Resistance and Metabolic Risk

In men with metabolic syndrome (hypogonadism + central obesity + insulin resistance), TRT consistently improves insulin sensitivity and reduces visceral fat. This is one of the clearest examples where treating hypogonadism removes a cardiovascular risk factor rather than adding one.

The bidirectional relationship matters: low testosterone worsens metabolic syndrome (low T → more visceral fat → more aromatization → more estrogen → more central adiposity). Treating hypogonadism breaks this cycle.

The Atrial Fibrillation Finding: How to Think About It

The AFib signal deserves nuanced framing, not minimization.

An absolute risk increase of ~1.1 percentage points over three years in a 63-year-old high-cardiovascular-risk population is clinically meaningful. AFib at baseline is already elevated in this demographic. Whether this risk applies to a 40-year-old with no prior cardiac history starting TRT is genuinely unknown.

What this means practically:

• If you have a history of AFib, supraventricular tachycardia, or other cardiac arrhythmia: discuss with your cardiologist before starting TRT.
• If you're at elevated AFib risk (older age, obesity, sleep apnea, hypertension, thyroid disease): include AFib symptom awareness in your monitoring picture.
• Symptoms to know: irregular heartbeat or palpitations, unexplained fatigue, shortness of breath, lightheadedness.
• AFib is treatable — awareness and monitoring converts a risk into a manageable variable.

For most men considering TRT who are under 55, metabolically healthy, and without cardiac history, the AFib signal in a high-risk elderly cohort is a background risk to be aware of, not a primary reason to avoid treatment.

Who Should Be Cautious: A Stratified View

Not all cardiovascular risk is the same. Here's a practical framework.

Men Who Should Discuss With a Cardiologist Before Starting TRT

Men Who Likely See Neutral-to-Favorable CV Risk Profile

Monitoring Protocol: What to Actually Track

Monitoring converts theoretical cardiovascular risk into a manageable, detectable variable. Here's the minimum standard.

The single most important safety variable is hematocrit. It's the one mechanism that directly converts TRT use into thrombotic risk (PE, DVT), and it's 100% detectable and manageable with standard bloodwork.

Men who do not get hematocrit checked in the first 3–6 months of TRT are the ones at real risk. Men who monitor it appropriately and act on elevated values are not in meaningful danger.

The FDA Warning: What It Still Says and What It Doesn't

The FDA's 2015 cardiovascular label update is still on all testosterone products. It reads: "Cardiovascular risk... reports of non-fatal myocardial infarction, non-fatal stroke, and cardiovascular death... consider the cardiovascular risks and benefits."

Critically: This was written before TRAVERSE. The FDA has not re-reviewed the label with TRAVERSE data incorporated. The Endocrine Society, the American Urological Association, and the International Society for Sexual Medicine have all updated their clinical practice guidelines post-TRAVERSE to reflect the non-inferiority MACE finding.

The label language reflects 2013–2015 signal; the clinical consensus reflects 2023 data. They're not yet synchronized.

What this means for you: the FDA label does not tell you TRT causes heart attacks. It tells you to discuss the risk with your provider — which you should do regardless.

The Bottom Line: What You Can Actually Say With Confidence

After TRAVERSE, here's the honest summary:

TRT does not increase the risk of heart attacks or strokes in men with confirmed hypogonadism, including men with pre-existing cardiovascular disease or high CVD risk. This is the strongest evidence the field has ever produced.

TRT is associated with a modestly higher rate of atrial fibrillation and pulmonary embolism. The absolute risk is small. The AFib signal was in an older, high-risk population. The PE risk is mechanistically linked to hematocrit elevation — which is monitorable and manageable.

The real cardiovascular risk of TRT is not heart attacks. It's elevated hematocrit → erythrocytosis → clot risk. This is the variable you should actually care about. It's also the one that standard bloodwork catches.

For most men under 55 with confirmed hypogonadism, no cardiac history, and a provider who monitors appropriately, the cardiovascular risk picture post-TRAVERSE is genuinely reassuring. This is not spin — it's the most rigorous data available.

If you're unsure whether TRT is the right path or whether a non-suppressive alternative (like enclomiphene) might fit your situation better, the quiz below helps clarify which approach fits your symptoms, labs, and risk profile.

Frequently Asked Questions

Q: Does the TRAVERSE trial prove TRT is completely safe for the heart? A: TRAVERSE showed that TRT is non-inferior to placebo for major cardiovascular events (heart attack, stroke, CV death) in high-risk men over ~3 years. It doesn't prove zero risk — it found real signals for atrial fibrillation and pulmonary embolism. "Safe" means manageable risk with monitoring, not the absence of any risk.

Q: I had a heart attack two years ago. Can I still use TRT? A: Possibly, but you need cardiology input first. TRAVERSE excluded men with acute cardiac events (within 6 months), so data in the early post-MI period is thin. Many cardiologists are now comfortable with TRT in stable post-MI patients who have confirmed hypogonadism — but the timing, dose, and monitoring plan should be coordinated with your cardiologist.

Q: Why did the FDA put a warning on TRT if TRAVERSE showed it was safe? A: The FDA warning was added in 2015 — eight years before TRAVERSE published. It was based on observational studies with significant methodological limitations. The clinical guidelines from endocrinology and urology societies have been updated post-TRAVERSE, but FDA label updates move more slowly.

Q: What's the biggest actual cardiovascular risk on TRT that I should monitor? A: Hematocrit elevation (erythrocytosis). This is the most direct modifiable risk factor — it raises blood viscosity and thrombotic risk. Get your hematocrit checked at 6–8 weeks, 3 months, and 6 months after starting TRT. If it exceeds 52%, dose adjustment or phlebotomy is indicated. Men with sleep apnea have additive risk and need earlier, more frequent checks.

Q: Does testosterone therapy raise blood pressure? A: Not significantly for most men at therapeutic doses. Some men experience minor transient fluid retention in the first 1–2 months (via estradiol-driven aldosterone activity), which can raise systolic BP by 1–3 mmHg temporarily. Men with pre-existing hypertension should monitor blood pressure at their usual frequency.

Q: Is testosterone injection safer for the heart than testosterone gel? A: The comparative cardiovascular data is limited, but the mechanism matters. Subcutaneous injections (daily or twice-weekly) produce more stable levels with lower peak-trough swings and are associated with smaller hematocrit elevations than once-weekly intramuscular injections. For men at elevated hematocrit risk (sleep apnea, elevated baseline hematocrit, prior DVT), a SubQ daily protocol is a reasonable harm-reduction consideration.

Q: I've heard some men with heart disease actually improved their cholesterol on TRT. Is that true? A: In men with metabolic syndrome and hypogonadism, TRT often improves triglycerides and may improve insulin sensitivity — both favorable metabolic effects. The HDL reduction (4–8%) is real but modest. Net lipid effect in metabolically unhealthy men is often neutral-to-favorable. In metabolically healthy men, the picture depends more on dose and delivery method.

Q: Should I choose enclomiphene instead of TRT if I'm worried about heart risk? A: Enclomiphene stimulates the pituitary to produce LH/FSH, which restores natural testosterone production without suppressing the HPG axis. It doesn't have the erythrocytosis or hematocrit-driven PE risk that injectable TRT carries (since your body's T production responds to endogenous feedback loops). For men with significant cardiovascular concern who are good SERM responders, it's a legitimate alternative to discuss. It's not appropriate for primary hypogonadism (damaged testes/HPG axis). The quiz can help clarify which path fits your situation.