Utilization and treatment patterns of subsidized gender affirming hormone therapy in Australian trans and gender diverse people from 2013–2023

Background Transgender and gender-diverse individuals use gender-affirming hormone therapy (GAHT) to induce affirming physical changes and improve psychosocial functioning. Limited longitudinal data exists describing GAHT formulations, doses, and individual-level use patterns.Aims To examine longitudinal utilization and treatment patterns in people initiating subsidized GAHT in Australia during 2013–2023.Methods We conducted a retrospective cohort study using a 10% random sample of Pharmaceutical Benefits Scheme (PBS) dispensing claims. Individuals aged 12–99 years were identified if initiating PBS-subsidized testosterone or estradiol with an incongruent gender marker or congruent gender marker, if updated. Outcomes included GAHT utilization, defined daily doses (DDD) over first treatment year, and longitudinal treatment regimens, stratified by sex recorded at birth (assigned male at birth [AMAB]; assigned female at birth [AFAB]).Results Among 2519 GAHT initiators (1487 AMAB; 1032 AFAB), median initiation age was 24 years (interquartile range [IQR]: 20–32). 30% (n = 763) updated their gender marker. Most AMAB individuals used estradiol tablets (n = 1197; 72.2%) and antiandrogens (n = 1197; 80.5%), while most AFAB individuals used testosterone undecanoate injections (n = 851; 82.5%). First-year mean estradiol DDDs increased from 1.43 to 1.60 DDDs; mean testosterone DDDs declined from 1.11 to 0.63 DDDs. AMAB individuals used more regimens (n = 6475; median 3) than AFAB individuals (n = 1845; median 1) over a median of 4.2 years (IQR: 2.4–6.8). Estradiol tablets were the most common AMAB starting regimen (n = 506; 34%), and estradiol tablets with an antiandrogen were most common overall (n = 1426; 22%). Testosterone undecanoate injections were the most common AFAB starting regimen (n = 594; 57.6%) and regimen overall (n = 964; 52.3%).Discussion The most common regimens were estradiol tablets with an antiandrogen in AMAB individuals and testosterone undecanoate injections in AFAB individuals. Over time, testosterone DDDs decreased, likely reflecting testosterone undecanoate dosing. Estradiol DDDs increased, though they were lower than expected. These findings offer insights into real-world GAHT utilization and treatment patterns, though further research is needed to optimize personalized care.