Recent progress in height management for trans adolescents

The widespread adoption of puberty-blocking medications for transgender youth has been life-changing, for the first time allowing trans people who are aware of their gender at a young age to avoid the need to reverse the unwanted and damaging changes of an inappropriate puberty, and instead acquire their desired secondary sexual characteristics directly. With this treatment, these youth experience an alleviation of their gender dysphoria with improved psychological functioning and overall well-being (de Vries et al., 2014), in contrast to the many psychosocial comorbidities commonly experienced by those who do not begin transition until adulthood.

However, even as puberty blockers have provided substantial benefits to trans youth, one area of physical development continues to pose challenges: height.

GnRH analogue medications used as puberty blockers temporarily and reversibly halt the body’s own production of testosterone or estrogen, preventing these sex hormones from producing the unwanted physical changes of natal puberty. As the presence of estrogen closes the growth plates of bones and prevents further gain of height (Shim, 2015), the use of puberty blockers – and the point in development at which cross-sex hormones are added – can affect the final adult height of trans adolescents.

This area is still a work in progress: many trans girls, even those on puberty blockers, may ultimately be substantially taller than is typical for cis women, while many trans boys may not reach a height typical of cisgender men. This issue has occasionally been mentioned in passing in the literature; Hembree (2011) notes that “Endocrine modifications may be used when final height may be less than or more than desired”, while Delemarre-van de Waal & Cohen-Kettenis (2006) note that delaying the closure of growth plates “may give the opportunity to manipulate growth”.

Recent poster abstracts have provided further detail on the extent of growth experienced by adolescent trans girls and boys on puberty blockers, as well as the results of hormonal methods of manipulating growth and final adult height. Catanzano & Butler (2018), studying trans adolescents being treated at the UK NHS’ Gender Identity Development Service, observed the outstanding issue with this treatment:

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.

Hellinga et al. (2019), treating trans youth at the VUmc gender clinic in the Netherlands, subsequently presented their clinical observations, noting that one cohort of 25 trans girls was found to have an average final height that was 1.9 standard deviations greater than that of Dutch cis women. In their case series of 11 trans girls, their average predicted adult height before estrogen was added to GnRH treatment was 3.6 standard deviations greater than that of Dutch cis women. However, their actual final height after the addition of estrogen was on average only 2.9 standard deviations greater. As this was still substantially greater than the typical height of cis women, the authors made the following recommendations for treatments to limit height further:

Further height reduction is feasible but may require adjustment of protocol. First, estrogens should be started at an earlier age. Second, the dosage of growth inhibiting effect of 17 beta estradiol should be increased or alternatively the synthetic estrogens should be used.

Pediatric endocrinologist Dr. Norman Spack has also previously mentioned a case in which estrogen was added at age 13 in order to reduce a trans girl’s final adult height from a predicted 6’5” to 5’11”.

Recent progress has been made in height management for trans boys as well. Grimstad & Jacobson (2019), treating trans youth at Children’s Mercy Hospital in Missouri, outline the problem facing trans boys: remaining on GnRH analogues while withholding testosterone for a lengthy period may be necessary in order to allow further gain of height, but excessively delaying hormonal transition and preventing them from experiencing male puberty at an appropriage age may be emotionally distressing.

In a case series of 31 trans boys, the authors administered oxandrolone, an anabolic steroid with androgenic effects. Crucially, unlike testosterone, the body cannot convert oxandrolone into estrogen via aromatization. Via this method, trans boys were able to obtain the desired masculinizing effects without the aromatization of testosterone closing growth plates and arresting their height. The authors note that 14 of these youth were already taller than their predicted adult height, with 5 being taller than their predicted height by at least 10.2 cm. They conclude:

This study highlights the importance of individualizing therapy in [transmasculine] youth with some patients possibly gaining additional height from non-aromatizable androgens.

These developments offer the hope of optimizing even more aspects of transition for trans adolescents. And even as puberty suppression has been revolutionary for a generation of trans youth, the outlook for those to come is getting better all the time. ■