Impact of Testosterone Therapy on Pulmonary Function in Transgender and Gender Expansive Individuals Assigned Female at Birth: A Cross-Sectional Comparative Study

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International Journal of Transgender Health

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Interpretation of pulmonary function tests (PFTs) currently uses normative data derived with a cisgender assumption for men and women, not taking into consideration transgender individuals who may have undergone interventions including hormonal therapy. If muscles involved for respiration change with exposure to testosterone therapy, normative PFT calculations for presumed cisgender individuals may not apply to transgender individuals. Thus, investigating pulmonary function in those who have undergone testosterone therapy will aid the accuracy of PFTs for this population.


Examine the potential impact of testosterone therapy on pulmonary function in gender expansive individuals assigned female at birth (AFAB) and complications of comparing PFT results against current normative data.


Primary outcomes were respiratory volume and strength, reflected by measures of forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1/FVC, maximum inspiratory pressure (MIP), and maximum expiratory pressure (MEP). Paired samples t-tests were performed between age- and race-matched pairs of 24 AFAB gender expansive individuals on testosterone therapy and 24 AFAB participants without a history of testosterone use.


Within-group comparison using Pearson correlation of individuals taking testosterone consistently for >1 year for gender-affirming purposes, yielded a moderate correlation for dosage and MIP of r(20) = 0.43, p = 0.049. Paired samples t-tests revealed highly significant differences in MEP (p = 0.001) and significant differences in FEV1/FVC (p = 0.026) for the testosterone use and no testosterone use groups. Percent predicted values for all measures were higher when analyzed using cisgender female normative data across both groups.


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