Reference Intervals for Biochemical Analytes in Transgender Individuals on Hormone Therapy

Background Hormone therapy in transgender individuals may impact processes that lead to changes in biochemical analytes, and therefore reference intervals. Currently, few reference interval studies are available for the transgender population. We determined biochemical reference intervals for transgender individuals receiving hormone therapy. Methods Our retrospective, laboratory-based, observational study included healthy transgender males ( N = 24) and transgender females ( N = 84) on hormone therapy. Various biochemical reference intervals were established for each cohort and compared to their cisgender counterparts. Results We detected significant differences in reference intervals for sodium, 139–142 mmol/L vs. 136–145 mmol/L when comparing transgender males (TM) with cisgender males (CM). The following significant changes in upper reference limits (URL) for TM versus CM were detected, ALP (URL: 96 U/L vs. 128 U/L), GGT (URL: 27 U/L vs. 67 U/L) and testosterone (URL: 46.7 nmol/L vs. 29.0 nmol/L), respectively. Moreover, when comparing transgender female (TF) to cisgender female (CF), significant differences in creatinine (URL: 117 μmol/L vs. 90 μmol/L), albumin (lower reference limit: 41 g/L, vs. 35 g/L), AST (URL: 50 U/L vs. 35 U/L), ALP (URL: 118 U/L vs. 98 U/L) and oestradiol (URL: 934 pmol/L vs. 213 pmol/L) were noted, respectively. Significantly higher LDL-C was observed for TM on hormone treatment, compared to baseline (2.9 mmol/L vs. 2.2 mmol/L, p <0.01). Conclusions Biochemical results for TM and TF receiving hormone therapy can be evaluated against our transgender-specific reference intervals for some analytes, while others can be compared to their identified gender reference intervals.