Last Updated: APRIL 2024

Men with total testosterone below 300 ng/dL experience a 2.4-fold increase in all-cause mortality, a risk largely driven by cardiovascular events (Shores et al., The Journal of Clinical Endocrinology & Metabolism, 2015). For decades, testosterone replacement therapy (TRT) has been a vital treatment for symptomatic hypogonadism. Despite its clear benefits for energy, libido, mood, and bone density, concerns about TRT’s impact on cardiovascular and cerebrovascular health have persisted. Recent robust clinical trials and regulatory updates have clarified this landscape, shifting the narrative from caution to cautious endorsement under proper medical supervision.

The Evolving Landscape of TRT Safety

Initial apprehension regarding TRT and cardiovascular risk emerged from a combination of older, often observational or underpowered studies, and post-market surveillance data. A 2013 study by Vigen et al. published in JAMA suggested an increased risk of stroke, myocardial infarction, and death in veterans undergoing TRT, particularly in older men or those with pre-existing cardiovascular disease. Similarly, the 2010 Basaria et al. study in The New England Journal of Medicine found a higher incidence of cardiovascular events in a cohort of elderly men with limited mobility treated with testosterone, leading to early termination of the study. These findings, while impactful at the time, were often criticized for methodological limitations, including retrospective design, lack of placebo control, and selection bias.

In response to these early signals, the U.S. Food and Drug Administration (FDA) issued a Drug Safety Communication in 2014, requiring labeling changes for all approved testosterone products to include information about potential cardiovascular risks. This led to a “black box warning” – the strongest safety warning the FDA can issue – on testosterone products, highlighting concerns about increased risk of stroke, heart attack, and death. This warning significantly influenced prescribing patterns and public perception for years.

The TRAVERSE Study: A Landmark Investigation

The definitive answer to the cardiovascular safety question came with the publication of the Testosterone Replacement Therapy for Assessment of Long-term Vascular Events and Efficacy Response in Hypogonadal Men (TRAVERSE) study in The New England Journal of Medicine in 2023. This prospective, randomized, double-blind, placebo-controlled trial enrolled over 5,200 men aged 45–80 years with pre-existing cardiovascular disease or high risk of it, and confirmed hypogonadism (two morning total testosterone levels below 300 ng/dL). Participants received either topical testosterone gel or placebo and were followed for an average of 33 months.

The primary endpoint of TRAVERSE was a composite of major adverse cardiovascular events (MACE), including nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death. The study conclusively demonstrated that testosterone therapy did not increase the risk of MACE compared to placebo. Specifically, the hazard ratio for MACE was 0.96 (95% confidence interval, 0.78 to 1.17), indicating no statistically significant increase in risk. Regarding cerebrovascular events directly, the incidence of nonfatal stroke was low and comparable between the testosterone and placebo groups.

“The TRAVERSE study provides robust evidence that testosterone replacement therapy, when administered to men with hypogonadism and a high risk of cardiovascular events, does not increase the risk of major adverse cardiovascular events,” concluded the study authors. This comprehensive trial, designed to address the very safety concerns that prompted the FDA warning, provided the high-quality, long-term data needed to re-evaluate TRT’s risk profile.

FDA’s Updated Stance

Following the compelling evidence from TRAVERSE and other post-market surveillance studies, the FDA re-evaluated its stance. In February 2025 (as referenced in Urology Times), the agency recommended the removal of the black box warning related to an increased risk of adverse cardiovascular outcomes for all testosterone products. This decision reflects a significant shift in understanding, aligning regulatory guidance with modern clinical evidence. Current literature now largely supports the conclusion that TRT does not significantly increase the risk of major cardiovascular events, including stroke, in men with hypogonadism when appropriately monitored.

Understanding Cerebrovascular Risk Factors on TRT

While TRT itself does not directly increase stroke risk, certain physiological changes that can occur during therapy warrant careful monitoring to mitigate potential cerebrovascular complications.

Hematocrit Elevation

The most recognized indirect risk factor on TRT is elevated hematocrit. Testosterone can stimulate erythropoiesis, increasing red blood cell production. Higher red blood cell count leads to increased blood viscosity, making blood thicker and less efficient at flowing through small vessels, including those in the brain. This increased viscosity raises the risk for venous thromboembolism (DVT, PE) and can impair cerebrovascular circulation, potentially leading to symptoms like brain fog, headaches, dizziness, and in severe cases, stroke.

Monitoring: Baseline hematocrit should be established. Monitoring should occur at 3–6 weeks, 3 months, 6 months, and then annually. Any change in testosterone dose or protocol requires resetting this monitoring schedule. The goal is typically to keep hematocrit below 52%.
Interventions: If hematocrit rises above 52%, a dose reduction (e.g., from 200mg testosterone cypionate per week to 100–140mg per week, or increasing injection frequency) is often the first step. Therapeutic phlebotomy (blood donation) can also be used to acutely lower hematocrit.
Overlooked Contributors: Sleep apnea (OSA) and dehydration are two commonly overlooked factors that can independently raise hematocrit. Screening for OSA before attributing all hematocrit elevation solely to testosterone dose is crucial, as is ensuring adequate hydration.

Blood Pressure

Some men may experience a slight increase in blood pressure on TRT. While not a direct cause of stroke, uncontrolled hypertension is a primary risk factor for cerebrovascular events. Regular blood pressure monitoring is essential, and any elevation should be managed through lifestyle changes or appropriate medication.

Estradiol (E2) Management

Testosterone aromatizes into estradiol (E2). While a healthy E2 level is crucial for men’s bone density, libido, and mood, excessively high E2 can lead to water retention, which may contribute to blood pressure elevation. Maintaining E2 within a physiological range (e.g., 20–40 pg/mL on TRT) is important. If E2 rises excessively, a small dose of an aromatase inhibitor like anastrozole (e.g., 0.25mg 2x/week) may be used, though dose reduction and increased injection frequency of testosterone are often preferred initial strategies to manage E2.

Optimizing TRT Protocols for Cardiovascular Health

Careful protocol design and consistent monitoring minimize risks while maximizing benefits. The goal is to achieve total testosterone levels typically between 600–900 ng/dL and free testosterone between 15–25 pg/mL, mimicking healthy physiological ranges. It is critical to note that the historical lower bound of 264 ng/dL for “low T” was calibrated from a 1970s population that included sick and elderly men, making it an inadequate threshold for defining symptomatic hypogonadism in many individuals.

Common Testosterone Esters

Testosterone Cypionate and Testosterone Enanthate are the most common injectable forms. Typical dosages range from 100–200mg per week. Splitting injections into smaller, more frequent doses (e.g., 50–100mg twice weekly) helps maintain stable hormone levels, reduce peak-and-trough fluctuations, and potentially mitigate estradiol conversion and hematocrit elevation.

Adjunctive Therapies

Human Chorionic Gonadotropin (HCG): Often prescribed alongside TRT (e.g., 500 IU 2-3x per week) to maintain testicular

TRT and Stroke Risk: What Current Studies Reveal