Is there a need for liver enzyme monitoring in people using gender-affirming hormone therapy?

Context: Individuals with gender dysphoria can receive gender-affirming hormone therapy. Different guidelines mention a severe risk of liver injury within the first months after the start of treatment with anabolic androgenic steroids, anti-androgens, and oral contraceptives, which is potentially fatal. Objective: The incidence of liver injury in a transgender population using gender-affirming hormone therapy. Design: Multicentre prospective study with 1933 transgender individuals, who started with hormone therapy between 2010 and 2020. Methods: The following parameters were analysed before hormone therapy, after 3 months, and after 12 months of hormone therapy: alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and gamma-glutamyltransferase (GGT). Both male and female reference values were considered. Liver injury was defined as either an elevation of 2? upper limit of normal (ULN) of ALP, 3? ULN of ALT, or 3? ULN of AST. Results: 889 transgender women and 1044 transgender men were included in the analysis. The incidence of liver injury within 12 months after the start of hormone therapy, without attribution to alcohol abuse, medical history, or comedication was 0.1 and 0.0%. in transgender women according to female and male reference intervals respectively, and 0.6 and 0.4% in transgender men (female and male reference intervals). Conclusion: The incidence of liver injury is found to be very low. We, therefore, conclude that liver enzyme monitoring within the frame of the risk of liver injury due to hormone therapy is not necessary for a transgender population.