ESPE Abstracts

Intro: Gender variance is becoming more common in young people. International guidelines recommend GnRH analogues (GnRHa) for gender variant young people from Tanner stage 2 onwards and cross-sex hormones (CSH) from age 16yr onwards. However, no good evidence exists how these affect growth. This first report aims to determine the impact of GnRHa and CSH on growth in young transgender adolescents to help inform prescribing in this patient cohort.

Methods: This is a prospective study of 44 young transgender people, attending the national Gender Identity Development Service early intervention clinic, on GnRHa for 1.3-3.8 years, transitioned to CSH treatment aged 16yr. 14 attained adult height (7 transgirls and 7 transboys) thus far. Changes in height and height velocity were calculated at each transition point.

Results: Seven transgirls, with a mean age at presentation of 12.5yr (range: 12-14; SD ± 0.8), started GnRHa at mean Tanner stage 3 (2-5±1.2), mean age 13yr (12.2 – 14.6±0.9) and CSH at mean age 16 yr (15.9 – 16.6±0.2); and 7 transboys all at Tanner stage 5, mean age at menarche 12yr (9-13±1.5), mean age at presentation of 14.2 yr (13.4 – 14.7±0.46), started GnRHa at mean age 15.1 yr (14.2 – 16.7±0.7) and CSH at mean age 16.5yr (15.8 – 17.7±0.3). Mean adult height was 180 cm (range: 167 – 190.1±7.2) in transgirls and 162.5 cm (range: 157.7 – 165.3±3) in transboys. Mean height velocity on GnRHa was 3.6 cm/yr (range: 0.03–5.5±1.8) in transgirls and 0.9 cm/yr (range: 0–2.2±0.7) in transboys. Mean height velocity on CSH for transgirls 3.5 cm/yr (range: 0.7–8.5±3) and 0.3 cm/yr (range: 0–0.8±0.3) for transboys. Mean total pubertal growth for transgirls was 16.8 cm (range: 1.2–24.2±7.7) and 2.3 cm (range: 0–4.2 cm ±1.6) for transboys.

Conclusion: Transboys did not show significant growth on GnRHa or CSH, but they were were older at presentationand all post-pubertal at start. Transgirls grew extensively on GnRHa and then unexpectedly only had modest growth when female puberty was induced with oestradiol. This may have arisen from the extension of the pre-pubertal growth phase leaving little growth potential. In some cases, this might challenge gender preferences as a taller final adult height could interfere more with “passing” in their preferred female gender. These are preliminary conclusions and further study is required.