Safety and efficacy of genderaffirming hormone therapy for transgender individuals

There has been a significant increase in demand for gender-affirming hormone therapy for transgender and gender diverse (trans) individuals over recent years. Current hormone regimens for trans individuals desiring masculinisation typically involve standard testosterone doses and formulations recommended for hypogonadal cisgender men, while trans individuals desiring feminisation are treated with estradiol with or without an antiandrogen. International consensus guidelines give recommendations for gender affirming hormone therapy regimens, though recommendations are largely based on expert opinion and there are currently limited data underlying the safety and efficacy in this population. The aim of this thesis is to evaluate the safety and efficacy of gender-affirming hormone therapy regimens. Our first aim was to investigate the influence of testosterone treatment, compared to no treatment, on gender dysphoria, depression, and suicidality in trans individuals desiring commencement of testosterone. This randomised controlled trial demonstrated that testosterone treatment significantly improved gender dysphoria, depression, and suicidality compared to the control group, supporting the use of testosterone in this population. We then evaluated serum testosterone concentrations and prescription patterns of transdermal testosterone in 2 retrospective cross-sectional analyses. Both 1% testosterone gel and 5% testosterone cream were commonly prescribed at doses lower than those recommended for cisgender hypogonadal men. There was a high proportion of individuals with a non-binary gender identity using both transdermal formulations. Transdermal testosterone was able to achieve serum testosterone concentrations recommended in consensus guidelines. The following study explored the risk of polycythaemia with different testosterone formulations. One in four individuals treated with intramuscular testosterone enanthate and one in six individuals treated with testosterone undecan