Background: Pubertal growth and adult height are important to many transgender adolescents undergoing medical transition. However, few studies are available on the impact of puberty suppression (PS) with GnRH analogues (GnRHa) and hormonal therapy (HT) with testosterone on growth. In this longitudinal cohort study, we investigated the effect of PS and HT on growth and adult height in transgender boys.
Methods: A total of 147 trans boys who were treated with GnRHa and testosterone, and had reached adult height were included. Data on height, bone age (BA) and parental height were collected. Height SDS was calculated based on female references. Mid-parental height was calculated and predicted adult height (PAH) was determined according to Bailey & Pinneau. The cohort was divided in those with growth potential (BA <14 years at start PS or, if BA was not available, menarche <1 year before start of PS, n=62) and those with little/no growth potential (n=85).
Results: In subjects with growth potential, PS resulted in a decrease of female height SDS from 0.1 ± 1.5 at baseline to -0.2 ± 1.0 at start HT, and a significant decrease in bone maturation. During HT, height SDS significantly increased by 0.4 SDS (95% CI 0.2 to 0.5). The difference between height SDS at start PS and adult height was 0.1 (95% CI -0.2 to 0.5). Mean adult height was 172.0 ± 6.8 cm (0.2 ± 1.1 SDS), which was 4.0 ± 6.0 cm above mid-parental height and 3.0 ± 3.6 cm above PAH at start of PS. A younger BA at start PS resulted in an adult height significantly further above PAH (1.2 cm/year; 95% CI 0.4 to 2.1). Individuals with little or no growth potential (n=85) reached a mean adult height of 169.0 ± 6.8 cm (height SDS -0.3 ± 1.1) and were significantly smaller than the group with growth potential at start PS.
Conclusion: Growth decelerated during GnRHa therapy and accelerated during HT. Although adult height SDS was similar to baseline, adult height was larger than predicted by BA at baseline. This effect was greater in those who started treatment at a younger BA. It is reassuring that PS and HT do not have a negative impact on adult height in trans boys and might even lead to a slightly taller adult height, especially in those who start at a younger age.
15 Sep 2022 - 17 Sep 2022