Context: Little is known about the effects of puberty suppression (PS) and hormone therapy (HT) on growth and adult height in transgender adolescents. These are topics of interest since height differs between sexes and some trans girls wish to limit their growth.

Aim: To investigate the influence of PS and HT on growth and the efficacy of growth reduction therapy in transgender girls.

Methods: A total of 161 trans girls treated with gonadotropin-releasing hormone agonists (GnRHa) and estrogen who had reached adult height were included. Height, parental height and bone age (BA) were recorded. Adult height was compared to predicted adult height (PAH) and to target height in three treatment groups (regular dose estradiol of 2mg, high dose estradiol of 6mg and 100-200ug ethinyl estradiol (EE)).

Results: During PS a decrease in growth velocity and bone maturation was observed. Trans girls treated with a regular estradiol dose reached an adult height of 180.8 ± 5.4 cm which was 2.2 ± 4.9 cm below PAH at start PS. Trans girls treated with a high dose estradiol and EE reached an adult height of 184.9 ± 5.7 cm and 180.1 ± 5.8 cm, respectively. When compared to subjects treated with a regular dose, adult height was 1.8 cm (95% CI -0.6 to 4.1) lower than PAH at start HT in trans girls treated with high dose estradiol and 4.1 cm (95% CI 0.6 to 7.6 cm) lower in trans girls treated with EE.

Conclusion: Treatment with GnRHa and estrogen resulted in an adult height that was slightly lower than predicted at the start of treatment. High doses of EE resulted in a significant growth reduction whereas high dose estradiol did not.