Thrombotic risk associated with gender-affirming hormone therapy.

Estrogen use in cisgender women is associated with well-established prothrombotic hemostatic changes.

• Estrogen use increases prothrombotic factors and decreases inhibitors of coagulation.
• Cisgender women using estrogen have an increased risk of thrombosis.
• These hemostatic parameter changes are described as 'well-established' in the literature.

Transgender women using estrogen appear to be at increased risk of both arterial and venous thrombosis.

• The risk may increase with longer time on estrogen.
• Studies of thrombosis risk in transgender people are described as 'less robust' than those in cisgender women.
• Some studies are limited by 'use of hormones and hormone management strategies that are no longer recommended.'
• The review covers both arterial and venous thrombosis outcomes.

Testosterone use in both cisgender and transgender men is associated with increases in hemoglobin and hematocrit.

• These increases can lead to erythrocytosis.
• Erythrocytosis resulting from testosterone use is associated with increased risk of thrombosis.
• This finding applies to both cisgender men and transgender men using testosterone.

Results of studies evaluating thrombosis risk in the setting of testosterone use are mixed.

• The review characterizes the evidence base for testosterone-associated thrombosis risk as producing mixed results.
• This contrasts with the more consistent findings for estrogen-associated thrombosis risk.
• The review covers exogenous testosterone use in the context of gender-affirming hormone therapy.

Understanding thrombosis risk associated with gender-affirming hormone therapy is essential for hematologists evaluating transgender and gender-expansive people.

• Hematologists may be asked to evaluate transgender and gender-expansive people and provide guidance on management.
• This includes guidance for those who may be at increased risk of thrombosis.
• Gender dysphoria is associated with negative health outcomes, making gender-affirming hormone therapy an important clinical consideration.
• The review covers both estrogen (for feminization) and testosterone (for masculinization) as components of gender-affirming hormone therapy.