Background : Transmasculine (TM) youth are able to access medical therapy for gender transition in greater numbers at earlier ages, navigating the options of puberty blocking GnRH analogs and androgen-based masculinizing gender affirming hormone therapy (GAHT). One reason to delay use of testosterone in these patients is to allow time for long bone growth prior to hormonally mediated closure of the epiphyseal plates. Delaying the use of testosterone in TM youth who are psychosocially ready for puberty and hormonal transition could add to emotional distress. In addition, TM youth may desire to maximize adult height. As a non-aromatizable androgen, oxandrolone cannot advance the bone age. In Turner syndrome patients, oxandrolone has been shown to augment adult height. The goal of this study was to begin to evaluate the effects of oxandrolone use in TM youth on growth and final height.
Methods : This was an IRB approved retrospective cohort study of TM youth seen at a pediatric academic medical center between 2013-2018 with the ICD diagnosis of gender dysphoria who were on oxandrolone therapy. Information regarding demographics and growth (including prior to therapy, while GnRH analogs, and while on each GAHT, including oxandrolone) were recorded, as well as duration on each therapy, mid parental heights (MPH) and current height.
Results : 34 patients received oxandrolone therapy at some point during their treatment. We focused on 31 of those patients (91.2%) on whom the MPH was known. Eleven of 31 (35.5%) were still growing. Although the mean current height in the TM youth was similar to their MPH (n=31, 0.1cm +/- 6.9 cm, mean +/- SD, not significant), 14/31 (45.2%) had already exceeded the predicted adult height. A small subset, 5/31 (16%) had exceeded the MPH by more than 10.2 cm (10.2, 10.2, 10.8, 13.1 14.9).
Conclusions : Based on evaluation relative to MPH, early data suggests that a subset of TM patients may benefit from a non-aromatizable androgen, as a subset of patients on oxandrolone appear to exceed their predicted heights. Patients who may benefit include those who are still growing and are eager to begin masculinization, those experiencing hot flashes on GnRH analogs, and those who have concerns about short stature. Future analysis will examine final adult heights in this patient population. This study highlights the importance of individualizing therapy in TM youth with some patients possibly gaining additional height from non-aromatizable androgens.