SAT416 The Incidence Of Autoimmune Disease In Transgender People After Initiation Of Gender-Affirming Hormone Therapy

Disclosure: C. Wiepjes: Advisory Board Member; Self; Novartis Pharmaceuticals. M. Den Heijer: None. Background Autoimmune diseases are more common in women than in men, possibly caused by differences in sex hormones. Generally, estrogen has an immunoenhancing effect, while testosterone has an immunosuppressive effect. However, it is not known whether gender-affirming hormone therapy in transgender people affects the risk of developing autoimmune diseases. Therefore, we aimed to compare the incidence of autoimmune diseases in trans women and trans men during hormone therapy with rates from the general population. Methods All people who visited the gender identity clinic in Amsterdam, the Netherlands, between 1972 and 2018 were included (n=8831). The medical records were screened for the occurrence of autoimmune diseases. In addition, the cohort was linked to a nationwide health data registry with medical diagnoses, as not all people received their check-ups at our clinic and in order to compare with a control population. These additional diagnoses were available from 2012-2017 and based on Diagnosis-Treatment-Combination codes. People were excluded for analyses if they did not use gender-affirming hormones (n=3022), did not have a follow-up visit (n=345), could not be linked with the nationwide health data registry (n=630), used alternating testosterone and estradiol (n=38), or had an autoimmune disease before start of hormone therapy (n=112). Standardized incidence ratios (SIR) were computed for trans women and trans men compared with the general population. Results In total, 4684 people were included, of which 2830 trans women and 1854 trans men. Median age at start of hormone therapy was 29 years (IQR 22 to 40) in trans women and 22 years (IQR 18 to 29) in trans men. Median follow-up time was 10 years (IQR 3 to 22, max 59) in trans women (total 38326 person years) and 4 years (IQR 1 to 13, max 48) in trans men (total 16548 person years). In total, 55 trans women and 48 trans men developed an autoimmune disease, after a median duration of hormone therapy of 7 years (IQR 2 to 17) in trans women and 5 years (IQR 1 to 12) in trans men. In the analyses with first autoimmune disease between 2012 and 2017, 25 trans women had an event, while 31 cases (SIR 0.81, 95%CI 0.52 to 1.16) were expected compared to cis men and 47 cases (SIR 0.54, 95%CI 0.35 to 0.77) compared to cis women. In trans men, 27 people had an event, while 15 cases were expected compared to cis men (SIR 1.81, 95%CI 1.19 to 2.55) and 23 cases were expected compared to cis women (SIR 1.16, 95%CI 0.77 to 1.64). Conclusion The risk of developing autoimmune diseases in trans women using gender-affirming hormones was similar to the risk in cis men, whereas trans men had a similar risk as cis women. This implies that gender-affirming hormone therapy does not influence the risk of developing autoimmune diseases. For further research it is interesting to see whether the severity of autoimmune diseases changes in trans people starting gender-affirming hormones. Presentation: Saturday, June 17, 2023