TRT and Heart Health: What the Latest 2025 Studies Reveal

The FDA removed the black box warning on testosterone products in February 2025. The decision hinged on TRAVERSE—a 5,204-patient randomized controlled trial that tracked men with hypogonadism for an average of 33 months. The primary endpoint was major adverse cardiac events: cardiovascular death, nonfatal heart attack, and nonfatal stroke. The testosterone arm showed 7.0% incidence versus 7.3% in placebo (hazard ratio 0.96, 95% CI 0.78-1.17). Non-inferior. The largest cardiovascular safety study in TRT history found no excess risk.

This contradicts a decade of regulatory fear. The 2014 FDA mandate that added cardiovascular warnings to every testosterone label was based on observational studies with survivor bias and confounding. TRAVERSE was designed specifically to answer whether replacement therapy increases heart risk in the exact population taking it—middle-aged and older men with documented testosterone deficiency. It didn't. But the nuance matters.

What TRAVERSE Actually Measured

The trial enrolled men 45-80 years old with two testosterone readings below 300 ng/dL and symptoms of hypogonadism. Participants had elevated cardiovascular risk at baseline—either pre-existing cardiovascular disease or multiple risk factors like hypertension, dyslipidemia, or obesity. Average exposure to testosterone was 22 months. This was not a young, healthy population experimenting with supraphysiologic doses. This was clinical replacement in men who needed it and had realistic cardiac risk profiles.

The testosterone group received gel titrated to achieve levels between 400-800 ng/dL. The comparison was placebo gel. Investigators tracked deaths, strokes, and myocardial infarctions through independent adjudication. The study was powered to detect a hazard ratio of 1.5—meaning a 50% increase in risk would have been statistically evident. It wasn't there. The confidence interval upper bound of 1.17 suggests that even if there is some small risk, it's nowhere near the magnitude that justified a black box warning.

TRAVERSE definitively settled the question for this population. Testosterone replacement therapy does not increase major adverse cardiac events in hypogonadal men with cardiovascular disease or high cardiovascular risk when dosed to achieve physiologic levels.

The Arrhythmia Signal

A 2025 meta-analysis of randomized controlled trials published alongside the FDA's label revision found a more than 50% increase in arrhythmia risk in men aged 40 and older receiving testosterone compared to placebo. This deserves attention. Arrhythmias were not the primary endpoint in TRAVERSE, and the meta-analysis pooled data across 41 trials with heterogeneous populations, doses, and follow-up periods.

The increased arrhythmia finding does not contradict TRAVERSE. Arrhythmias—primarily atrial fibrillation—can occur without progressing to stroke or death, especially when managed. The relevant question is whether this risk translates into hard outcomes. TRAVERSE showed it does not in the aggregate. But individual patients with pre-existing arrhythmia or structural heart disease may experience different risk-benefit calculations. This is where clinical judgment and monitoring separate competent care from protocol-driven medicine.

Testosterone increases hematocrit. Higher hematocrit increases blood viscosity. Increased viscosity can theoretically elevate stroke risk, particularly in men with atrial fibrillation who are not anticoagulated. The arrhythmia signal may represent a subset effect—patients who develop atrial fibrillation on TRT and are not adequately monitored or treated. The solution is not to withhold testosterone. The solution is to monitor hematocrit and screen for arrhythmia in at-risk patients.

Who Has Elevated Risk

TRAVERSE enrolled men with existing cardiovascular disease or multiple risk factors. The trial was designed to stress-test TRT safety in a high-risk cohort. It passed. But specific subgroups within that population may still have differential risk. Men with untreated sleep apnea, uncontrolled hypertension, baseline hematocrit above 50%, or history of atrial fibrillation are not categorically excluded from TRT—but they require closer monitoring and risk mitigation.

Sleep apnea is particularly relevant. Obstructive sleep apnea increases both cardiovascular risk and baseline testosterone suppression. TRT can worsen untreated sleep apnea by increasing upper airway tissue mass and reducing central respiratory drive during sleep. A 2019 study from Brigham and Women's Hospital found that testosterone therapy in men with moderate to severe untreated sleep apnea worsened apnea-hypopnea index scores and nocturnal oxygen desaturation. The intervention is not to deny TRT—it's to treat the sleep apnea first with CPAP or mandibular advancement devices, then initiate testosterone.

Men with baseline hematocrit above 50% are at higher risk for polycythemia on TRT. Polycythemia increases thrombotic risk. Guidelines vary, but most clinicians pause or reduce testosterone dosing when hematocrit exceeds 54%. Some donate blood to manage levels. Others switch from injectable to transdermal formulations, which produce smaller peaks and less hematocrit stimulation. The point is that hematocrit is a modifiable risk factor. Elevated hematocrit is not an argument against TRT—it's an argument for dose adjustment and monitoring.

How to Monitor Cardiovascular Risk on TRT

Baseline labs before initiating TRT should include hematocrit, lipid panel, fasting glucose or HbA1c, and blood pressure measurement. An ECG is reasonable in men over 50 or those with known cardiovascular disease. These establish a reference point. The goal is not to screen out patients—it's to identify risk factors that need concurrent management.

Hematocrit should be rechecked 3-6 months after starting TRT and then every 6-12 months. If levels exceed 54%, dose reduction or temporary cessation is standard practice. Some patients will normalize with dose adjustment. Others may require phlebotomy or switching formulations. Injectable testosterone produces higher peaks and greater hematocrit stimulation than gels or pellets. Patients with baseline hematocrit in the high-normal range (48-50%) may benefit from starting with transdermal administration.

Blood pressure should be monitored at each follow-up. Testosterone can cause mild sodium retention and increase blood pressure in some men, particularly those with pre-existing hypertension. A 2018 meta-analysis from the University of Western Australia found that TRT increased systolic blood pressure by an average of 1.91 mmHg—clinically insignificant in normotensive men but potentially relevant in uncontrolled hypertensives. Blood pressure elevation on TRT is manageable with standard antihypertensive therapy. It is not a contraindication.

Lipid panels should be repeated 3-6 months after initiation and annually thereafter. Testosterone replacement typically lowers HDL cholesterol modestly (2-5 mg/dL) and may reduce triglycerides. The effect on LDL is variable. The clinical significance of a small HDL reduction in the context of improved body composition, insulin sensitivity, and symptom relief is unclear. What matters is overall cardiovascular risk, not isolated lipid changes. Statins remain effective in men on TRT.

Atrial fibrillation screening is not routine but should be considered in men over 65, those with structural heart disease, or anyone reporting palpitations or irregular heartbeat. A baseline ECG and periodic pulse checks are low-cost, high-yield. If atrial fibrillation develops on TRT, anticoagulation decisions follow standard CHA2DS2-VASc scoring. The presence of atrial fibrillation does not automatically disqualify a patient from continued TRT, but it does shift the risk calculus and may warrant cardiology consultation.

What the 2025 Data Means Clinically

The removal of the black box warning reflects what the evidence has shown for years—testosterone replacement at physiologic doses does not increase cardiovascular mortality in hypogonadal men. The TRAVERSE trial was conservatively designed. It enrolled high-risk men. It tracked them for nearly three years. It found no signal. The arrhythmia meta-analysis adds a layer of specificity: monitor for atrial fibrillation, particularly in older men or those with structural heart disease. Manage hematocrit. Control blood pressure. These are standard elements of competent TRT management, not revelations.

The implication is that the cardiovascular concerns that have limited TRT access were overstated. The 2014 FDA warning was premature. It was based on flawed observational data that confused association with causation and failed to account for indication bias—sicker men are more likely to be prescribed testosterone and more likely to have cardiac events regardless of treatment. TRAVERSE corrected the record. The regulatory system is catching up.

For clinicians, this means evidence-based discussions with patients. Cardiovascular disease is not a contraindication to TRT. It's a reason to monitor more carefully. Men with testosterone deficiency and heart disease may benefit from replacement therapy—improved exercise tolerance, reduced visceral fat, better glycemic control. The cardiovascular risk profile is neutral to favorable when managed appropriately. The 2025 research clarifies what should have been obvious: treating a hormone deficiency is not the same as administering a cardiotoxic drug.

Remaining Questions

TRAVERSE followed men for an average of 33 months. Longer-term data would be useful, particularly for men who start TRT in their 40s and remain on it for decades. The trial used testosterone gel. Injectable esters produce different pharmacokinetics—higher peaks, lower troughs—and may have different cardiovascular effects. No large-scale RCT has compared formulations head-to-head for cardiovascular outcomes.

The arrhythmia signal warrants mechanistic investigation. Is it a direct electrophysiologic effect of testosterone? Is it mediated through hematocrit or blood pressure changes? Is it confined to specific subgroups? These questions matter for refining patient selection and monitoring protocols. The absence of increased MACE in TRAVERSE suggests that even if arrhythmia risk is real, it's either rare or clinically manageable. But granular data would improve care.

The trial excluded men with recent cardiac events (within six months) and those with severe heart failure. This is appropriate for a safety trial, but it leaves uncertainty about TRT use in acute post-MI or decompensated heart failure settings. Some observational data suggests testosterone may improve outcomes in chronic heart failure, but RCT evidence is limited. The conservative approach is to stabilize acute cardiac conditions before initiating TRT, but the evidence gap remains.

The 2025 research landscape on TRT and cardiovascular risk is clearer than it has ever been. The black box warning is gone. The largest RCT showed no increased MACE. A meta-analysis flagged arrhythmia as a monitoring point. The synthesis is straightforward: testosterone replacement therapy is cardiovascularly safe in hypogonadal men when dosed appropriately and monitored competently. The era of blanket cardiovascular contraindications is over. What remains is individualized risk assessment and evidence-based management.