Testosterone concentrations and prescription patterns of 1% testosterone gel in transgender and gender diverse individuals.

Background: Masculinising hormone therapy with testosterone is used to align an individual's physical characteristics with their gender identity. Standard testosterone doses and formulations recommended for hypogonadal cisgender men are typically administered, although there are currently limited data evaluating the use of 1% testosterone gel in gender-affirming hormone therapy regimens.

Objectives: The objective of the study was to assess the prescription patterns and serum total testosterone concentrations achieved with 1% testosterone gel in trans and gender diverse individuals.

Materials and methods: A retrospective cross-sectional analysis was undertaken of trans individuals at a primary and secondary care clinic in Melbourne, Australia. Sixty-seven individuals treated with 1% testosterone gel were included. Primary outcomes were testosterone dose and serum total testosterone concentration achieved.

Results: Median age was 25 (22-30) years and median duration of testosterone therapy was 12 (7-40) months. Thirty-five (52%) individuals had a nonbinary gender identity. Initial median testosterone dose was 25 mg (12.5-31.3) daily. Fifty-two (78%) individuals commenced doses <50 mg daily, the recommended starting dose for hypogonadal cisgender men. Median total testosterone concentration achieved was 11.9 nmol/l (7.3-18.6). Polycythaemia (haematocrit >0.5) was documented in eight of 138 (6%) laboratory results in six individuals.

Discussion and conclusions: One percent testosterone gel achieves serum total testosterone concentrations in the cisgender male reference range. A high proportion of individuals had a nonbinary gender identity and most individuals commenced a lower dose than that typically administered to hypogonadal cisgender men, potentially related to slow or 'partial' masculinisation goals.