The conducting airways before and after gender-affirming hormone therapy in transgender individuals

On average, females have smaller airways than males. The largest discrepancy in airway size occurs during puberty, when endogenous sex hormone concentrations diverge between males and females. Transgender individuals often use gender-affirming hormone therapy (GAHT) to align physical characteristics with gender identity. It is unknown whether GAHT influences airway size (luminal area and length). We evaluated the large conducting airways before starting GAHT and while undergoing years of GAHT. This retrospective within-subject study included 12 adult transgender individuals who underwent CT scanning before starting GAHT and again after ≥1 year of GAHT. For each transgender individual, we identified two matched cisgender controls (one male and one female) who also underwent two CT scans over a comparable time interval for longitudinal comparison. We used a three-dimensional reconstruction of CT imaging to measure luminal areas. Within-subject changes in airway size between scans were assessed using Student's paired t-tests in transgender individuals undergoing feminizing hormone therapy. Variance between scans was assessed using Levene's test. Pre-scans occurred an average of 2.0 ± 3.1 years before beginning GAHT. Transgender persons were on GAHT for an average of 3.3 ± 1.7 years (range, 1.0 - 6.7 years) at their second scan. We found no significant differences in airway luminal cross-sectional areas for transgender persons on feminizing hormone therapy. The variance in airway size change between scans was not statistically different between transgender individuals and control subjects. Our findings suggest that the size of large conducting airways might remain unchanged after a period (>1 year) on GAHT.