Tracking Epigenetic Biomarkers of Health and Aging During the Initial Year of Gender-Affirming Hormone Therapy.

Gender-affirming hormone therapy (GAHT) is a necessary treatment for many transgender people, and there is a critical need to further improve treatment experience and mitigate possible risks. Here we investigated whether DNA methylation (DNAm) biomarkers of health and aging are modified during the first year of GAHT and whether these vary by treatment type. Cohort consisted of 13 trans women (TW) and 13 trans men (TM). Sampling occurred at baseline (pre-GAHT), and at 6- and 12-month follow-up. We tracked the longitudinal dynamics of three epigenetic clocks (Horvath, Hannum, PhenoAge), DNA methylation-based telomere length (DNAmTL), and DunedinPACE. At baseline, the Horvath and Hannum showed accelerated epigenetic aging, particularly pronounced among TM, while the PhenoAge and DunedinPACE showed lower pace of aging in both groups. This discrepancy may reflect possible effects of minority stress in an otherwise healthy cohort. While GAHT did not affect the three clocks, DNAmTL and DunedinPACE showed treatment-specific patterns but with notable inter-individual variability in trajectories. TW had increased DunedinPACE (estimate = 0.057, p=0.002) and slight DNAmTL gains (estimate = 0.024, ns); TM exhibited stable to slight decline in DunedinPACE (estimate = -0.013, ns), and reduction in DNAmTL (estimate = -0.057, p=0.037). The marked heterogeneity is indicative of an individualized response to treatment and highlights the potential value of incorporating such biomarkers in comprehensive health monitoring. Our findings emphasize the need for larger, long-term studies to optimize personalized strategies for gender-affirming healthcare.