Many transgender youth experience gender dysphoria, a risk factor for suicide. Gender-affirming hormone therapy (GAHT) ameliorates this risk but may increase the risk for thrombosis, as seen from studies in adults. The aim with this study was to examine thrombosis and thrombosis risk factors among an exclusively adolescent and young adult transgender population.


This retrospective chart review was conducted at a pediatric hospital-associated transgender health clinic. The primary outcome was incidence of arterial or venous thrombosis during GAHT. Secondary measures included the prevalence of thrombosis risk factors.


Among 611 participants, 28.8% were transgender women and 68.1% were transgender men. Median age was 17 years at GAHT initiation. Median follow-up time was 554 and 577 days for estrogen and testosterone users, respectively. Individuals starting GAHT had estradiol and testosterone levels titrated to physiologic normal. Multiple thrombotic risk factors were noted among the cohort, including obesity, tobacco use, and personal and family history of thrombosis. Seventeen youth with risk factors for thrombosis were referred for hematologic evaluation. Five individuals were treated with anticoagulation during GAHT: 2 with a previous thrombosis and 3 for thromboprophylaxis. No participant developed thrombosis while on GAHT.


In this study, we examined thrombosis and thrombosis risk factors in an exclusively adolescent and young adult population of transgender people receiving GAHT. These data suggest that GAHT in youth, titrated within physiologic range, does not carry a significant risk of thrombosis in the short-term, even with the presence of preexisting thrombosis risk factors.

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