TRT and Pulmonary Embolism: Understanding the Risk

Written by Adam Maggio | Medically reviewed by Dr. Sarah Chen, PharmD, BCPS

Pulmonary embolism (PE), a serious condition where a blood clot blocks an artery in the lungs, is a recognized, albeit rare, potential risk associated with testosterone replacement therapy (TRT). While large-scale studies like TRAVERSE have shown a small but statistically significant increase in PE incidence, careful patient selection, monitoring for polycythemia, and prompt recognition of symptoms are crucial for minimizing this risk.

TRT and Pulmonary Embolism: What You Need to Know About This Serious Risk

Pulmonary embolism (PE) is a life-threatening condition that occurs when a blood clot, often originating from a deep vein thrombosis (DVT) in the legs, travels to the lungs and blocks one or more pulmonary arteries. For men considering or undergoing testosterone replacement therapy (TRT), the potential risk of PE is a serious concern that warrants careful consideration and discussion with your physician. While rare, it's a complication that has been consistently observed in some studies.

Evidence Linking TRT to PE Risk

The relationship between TRT and PE risk has been a subject of intense scrutiny. One of the most significant pieces of evidence comes from the large, FDA-mandated TRAVERSE trial (Lincoff et al., 2023). This study, designed to assess the cardiovascular safety of TRT, reported a statistically significant higher incidence of pulmonary embolism in the testosterone group (0.9%) compared to the placebo group (0.5%). While the absolute difference was small, the finding was notable given the trial's robust design and large patient population.

Other studies have also highlighted this association. A meta-analysis by Houghton et al. (2018) and a population-based case-control study by Martinez et al. (2016) both suggested an increased risk of venous thromboembolism (VTE), which includes PE, particularly during the initial months of TRT. Conversely, some retrospective analyses, such as one by Sharma et al. (2016) using Veterans Administration data, did not find a significant association between TRT and DVT/PE risk in men with low testosterone. This conflicting data underscores the complexity of the issue and the importance of individualized risk assessment.

Potential Mechanisms of Increased Risk

The primary mechanism believed to link TRT to an increased risk of PE is its effect on red blood cell production, leading to polycythemia (also known as erythrocytosis). As discussed in the previous article, testosterone stimulates the production of red blood cells, which can result in an elevated hematocrit (the percentage of red blood cells in the blood). When hematocrit levels become too high (typically above 52-54%), the blood becomes thicker and more viscous, increasing the likelihood of clot formation. These clots can then dislodge and travel to the lungs, causing a PE.

Other potential, though less definitively established, mechanisms include testosterone's influence on platelet aggregation and various coagulation factors. However, the most consistent and clinically relevant link remains polycythemia.

Identifying and Mitigating Risk

Given the potential for PE, careful patient selection and rigorous monitoring are paramount for men on TRT:

• Comprehensive Risk Assessment: Before initiating TRT, your doctor should conduct a thorough evaluation of your personal and family history of blood clots, including DVT and PE. Any pre-existing conditions that increase clotting risk (e.g., inherited thrombophilias, active cancer, prolonged immobility, severe obesity) must be carefully considered.
• Hematocrit Monitoring: Regular monitoring of hematocrit levels is essential. Typically, this involves checks at 3-6 months after starting TRT, and then every 6-12 months thereafter. If hematocrit rises above the target range (e.g., >52%), interventions such as dose reduction, changing the route of administration, or therapeutic phlebotomy (blood donation) should be implemented promptly to reduce the risk of hyperviscosity.
• Patient Education: You must be educated about the symptoms of PE, which can include sudden shortness of breath, chest pain (especially with deep breaths), rapid heart rate, coughing (sometimes with blood), and dizziness. Unlike the more subtle symptoms of DVT, PE symptoms are often acute and severe, requiring immediate medical attention.
• Caution in High-Risk Individuals: For men with a history of VTE or known thrombophilia, the decision to initiate TRT should be made with extreme caution, often involving consultation with a hematologist or other specialists. In some cases, TRT may be contraindicated.

Unlike the general cardiovascular safety, which appears neutral for MACE, the specific signal for PE with TRT is a concern that requires proactive management. It's not a reason to avoid TRT if indicated, but a reason to be vigilant.

Practical Takeaway

Pulmonary embolism is a serious, though uncommon, risk associated with TRT that you need to be aware of. Your doctor will carefully assess your risk factors before starting therapy and will monitor your blood tests, especially your hematocrit, regularly. If your hematocrit gets too high, adjustments to your TRT or therapeutic phlebotomy will be necessary to reduce your risk of blood clots. Most importantly, if you experience sudden shortness of breath, chest pain, or a rapid heartbeat while on TRT, seek immediate medical attention. Don't delay; early recognition and treatment are vital for PE.