Hemostatic parameters in transgender women receiving gender-affirming hormone therapy: A shift to a cisgender female pattern?

Transgender women have an increased incidence of venous thromboembolism (VTE) compared with cisgender individuals. However, data on hemostatic parameters in this population are scarce. We aimed to evaluate hemostatic parameters in transgender women receiving gender-affirming hormone therapy (GAHT) compared with cisgender controls. We conducted a cross-sectional study including 40 transgender women (sample size based on prior calculation), and age- and body mass index-matched cisgender women (n = 25) and cisgender men (n = 25) as controls. Blood samples were collected between 2016 and 2023. We assessed hemostatic parameters (plasminogen activator inhibitor-1 [PAI-1], free protein S, vascular cell adhesion molecule-1, antithrombin, anticoagulant protein C, prothrombin time activity, thrombin time), hormonal profile (estradiol, sex hormone-binding globulin, estrogen dose, total testosterone, and free androgen index), and inflammatory markers (fibrinogen, C-reactive protein, and leukocyte count). Transgender women (mean [SD] age, 30.6 [8.0] years; median GAHT duration, 36.5 months) and cisgender women had similar hemostatic and inflammatory parameters. Compared with cisgender men, transgender women had higher PAI-1 levels (p = 0.001) and lower free protein S levels (p = 0.023). No differences were found in other hemostatic parameters between the groups. In conclusion, transgender women on long-term GAHT had higher levels of PAI-1 and lower levels of free protein S than cisgender men, indicating a slightly more prothrombotic profile. However, their hemostatic and inflammatory parameters were similar to those of cisgender women, suggesting a shift towards a female pattern. Factors beyond GAHT may contribute to the increased risk of VTE in this population.