Bone Density in Transgender Youth on Gender-Affirming Hormone Therapy

Some transgender youth are treated with gonadotropin-releasing hormone agonists (GnRHa) followed by testosterone or estradiol, which may impact bone mineral density (BMD). This cross-sectional study of transgender youth (n = 56, aged 10.4-19.8 years, 53% assigned female at birth [AFAB]) utilized total body dual-energy x-ray absorptiometry to evaluate BMD Z-scores, and associations between GnRHa duration, body mass index (BMI), and BMD. Participants on GnRHa alone (n = 19, 14 assigned male at birth [AMAB], 5 AFAB) at the time of the study visit were 13.8 [12.8, 15.3] (median [IQR]) years old, had been on GnRHa for 10 [5.5, 19.5] months, and began GnRHa at age 12 [10.4, 12.6] years. Total body BMD Z-score for individuals on GnRHa monotherapy was -0.10 [-0.8, 0.4] (AFAB, female norms) and -0.65 [-1.4, 0.22] (AMAB, male norms). AFAB participants (n = 21) on testosterone were age 16.7 [15.9, 17.8] years, had been on testosterone for 11 [7.3, 14.5] months, and started testosterone at age 16 [14.8, 16.8] years; total body BMD Z-score -0.2 [-0.5, 0] (male norms) and 0.4 [-0.2, 0.7] (female norms). AMAB participants (n = 16) were age 16.2 [15.1, 17.4] years, had been on estradiol for 11 [5.6, 13.7] months, and started estradiol at age 16 [14.4, 16.7] years; total body BMD Z-score -0.4 [-1.1, 0.3] (male norms) and -0.2 [-0.7, 0.6] (female norms). BMD Z-score was negatively correlated with GnRHa duration (male norms: r = -0.5, P = .005; female norms: r = -0.4, P = .029) and positively correlated with BMI (male norms: r = 0.4, P = .003; female norms: r = 0.4, P = .004). In this cross-sectional cohort, total body BMD Z-scores were slightly below average, but lowest in the AMAB group on GnRHa monotherapy.