Background: Gender affirming hormone treatment (GAHT) results in measurable changes to anthropomorphic, biochemical and hormonal variables that are important to patients and their health care professionals to guide treatment. This study sought to quantify changes which occur in response to initiation of GAHT.
Methods: We performed a retrospective cohort study of outcomes in transgender and gender diverse patients starting GAHT across three practices in Sydney, Australia. The primary study outcome was time required to achieve optimal hormone levels after commencement of GAHT. Additional analyses were performed to assess whether specific clinical and biochemical factors were associated with an improved likelihood of achieving target hormone levels.
Results: A total of 346 patients were included with a median follow-up of 11 months. Among 154 transmasculine individuals, 116 (75%) achieved a target testosterone level of >10 nmol/L during follow-up. No clinical or biochemical factors were significantly associated with likelihood of reaching therapeutic testosterone concentrations. Among 192 transfeminine individuals, 131 (71%) achieved a target testosterone level of <2.0 nmol/L during follow-up. Factors associated with an increased likelihood of adequate testosterone suppression were use of subdermal estradiol implants as well as cyproterone acetate as an androgen antagonist. Changes in differing directions were observed during repeated measures of lipids, liver function, and blood count between transmasculine and transfeminine individuals, reflecting the important effects of testosterone and estradiol on biochemical tests ordered as part of routine clinical care.
Conclusions: Most (>70%) TGD patients will achieve target testosterone levels within 9 months of GAHT initiation. Adverse effects of GAHT such as polycythemia, hyperkalemia and hyperprolactinemia are exceedingly rare, and when they occur are usually mild.