There may be significant cardiovascular risks associated with hormone replacement therapy for people with gender dysphoria, according to new data to be presented at the American College of Cardiology’s upcoming annual meeting, ACC.23 Together with the World Congress of Cardiology, in New Orleans.

Specifically, individuals with gender dysphoria who received hormone therapy—typically in the form of estrogen for people assigned male at birth or testosterone for people assigned female at birth—had higher rates of ischemic stroke, ST elevation myocardial infarction, and pulmonary embolism. However, hormone therapy replacements were not associated with a higher risk of death. 

The most likely explanation for the increased risk of cardiovascular events, researchers said, is increased clotting activity in the blood. This is a known to be a side effect of taking estrogen or testosterone.

The findings are based on an examination of hospital records for over 21,000 people with gender dysphoria, including more than 1,675 people who had taken hormone replacement therapy. For the purpose of the analysis, all patients who had taken any type of hormone replacements at any time were grouped together, without taking into account the duration of treatment or the age at which treatment was initiated. These nuances could potentially be explored further in future studies, the researchers noted. 

Aiding fully-informed decisions to begin hormone replacement therapy

Acknowledging that hormone therapy has risen among people who identify as transgender in the United States in recent years—especially among teens and young adults—the researchers explain that their work helps raise awareness of potential trade-offs, making sure that patients are fully informed before starting treatment.