Endocrine Abstracts

Gonadotropin-releasing hormone analogues (GnRHa) are prescribed to adolescents with gender dysphoria under age 15 who have reached Tanner stage 2/3 to prevent progression through puberty and allow them time to consider their gender identity. The possible effects of the therapy on the pubertal growth spurt are poorly understood. A height more congruent with their identified gender is desired by transgender individuals, thus it is crucial that they are fully informed of its potential impact when consenting to the therapy. SuperImposition by Translation and Rotation (SITAR) growth curve analysis was used to study the pubertal growth spurt in transgender individuals on GnRHa therapy. SITAR is a nonlinear mixed effects growth model that estimates the age at peak height velocity (APV) and peak height velocity (PHV) in individuals. This was a retrospective observational study using patient records. SITAR analysis was applied separately to groups of transboys (n=35) and transgirls (n=34). The growth of cis-gender females (n=70) and males (n=54) recorded during the longitudinal Chard Growth Study (Cole et al., 2015) was modelled and used for comparison. The majority of transboys presented post-menarche, in the later stages of their pubertal growth spurt, thus the impact of GnRHa therapy was minimal. In transgirls the APV was not delayed but the PHV was reduced resulting in less pubertal growth. Further growth after the pubertal spurt occurred in both groups, and in transboys it could be attributed to the initiation of cross-sex hormone therapy. This study offers evidence that GnRHa therapy may alter the dynamics of the pubertal growth spurt, particularly in transgirls so care needs to be exercised as to the timing of the treatments. Finally, an extended growth spurt is seen after age 16 years, concomitant with the starting of cross sex hormone treatment which may have an enhancing effect on final height in transgender individuals.

COLE, T. J., 2015. The relationship between Insulin-like Growth Factor 1, sex steroids and timing of the pubertal growth spurt. Clinical Endocrinology, 82, 862-869.