Pubertal Suppression in Early Puberty Followed by Testosterone Mildly Increases Final Height in Transmasculine Youth

Context: Treatment for transmasculine youth (TMY) can involve testosterone treatment and is sometimes preceded by gonadotropin-releasing hormone agonist (GnRHa) treatment for puberty blockade. GnRHas can increase final height in birth-assigned females with central precocious puberty. Maximizing final adult height (FAH) is an important outcome for many TMY. Objective: Our objective was to determine how GnRHa treatment before testosterone impacts FAH. Methods: Retrospective cohort study at 5 US transgender health clinics. Participants were 32 TMY treated with GnRHas in early to midpuberty before testosterone (GnRHa + T group) and 62 late/postpubertal TMY treated with testosterone only (T-only group). Results: The difference between FAH minus midparental target height (MPTH) was +2.3 ± 5.7 cm and −2.2 ± 5.6 cm in the GnRHa + T and T-only groups, respectively (P < .01). In the GnRHa + T group, FAH was 1.8 ± 3.4 cm greater than predicted adult height (PAH) (P < .05) and FAH vs initial height (IH) z-score was 0.5 ± 1.2 vs 0.16 ± 1.0 (P < .05). After adjusting for patient characteristics, each additional month of GnRHa monotherapy increased FAH by 0.59 cm (95% CI 0.31, 0.9 cm), stage 3 breast development at start of GnRHa was associated with 6.5 cm lower FAH compared with stage 2 (95% CI −10.43, −2.55), and FAH was 7.95 cm greater in the GnRHa + T group than in T-only group (95% CI −10.85, −5.06). Conclusion: Treatment with GnRHa in TMY in early puberty before testosterone increases FAH compared with MPTH, PAH, IH, and TMY who only received testosterone in late/postpuberty. TMY considering GnRHas should be counseled that GnRHas may mildly increase their FAH if started early.