Puberty blockers can be beneficial for trans girls even in late adolescence

Zinnia JonesGuidelines for the treatment of trans adolescents with puberty blockers and cross-sex hormones recommend that puberty blockers should be initiated once the first physical changes of natal puberty, Tanner stage 2, have begun (Hembree et al., 2017). However, in practice, many trans adolescents do not begin treatment until the final pubertal stages of 4 or 5, after having already experienced many of the undesired physical changes associated with their birth-assigned sex. For instance, Tack et al. (2016) report using the androgenic progestin lynestrenol instead of GnRH analogues for trans boys who have already reached stage 4 or later of their natal puberty, while Tack et al. (2017) note the substitution of the antiandrogen cyproterone acetate as a puberty blocker for trans girls who begin treatment at stage 4 or later.

I’ve also recently covered the area of height management of trans adolescents during transition treatment; even with the use of puberty blockers, trans girls may reach a final adult height substantially greater than that which is typical of adult cis women, while trans boys may only achieve a below-average height in comparison to adult cis men. In newer studies, the administration of higher-dose estrogen at earlier ages has been recommended to halt the growth of trans girls, while the androgenic steroid oxandrolone was used in place of testosterone in trans boys due to its inability to convert to estradiol and prematurely fuse bone growth plates.

However, Ghelani et al. (2020) have recently published results finding that puberty blockers can have a beneficial effect on height in adolescent trans girls even when started at Tanner stage 4 or 5 of their natal puberty. The 11 trans girls in the study were administered GnRH analogues at a mean age of 16.4 years plus or minus 0.66 years, with their height, weight, and lean (fat-free) mass being measured at 0, 6, and 12 months after starting treatment. Over that time, their standard deviation score for height compared to reference populations of the same age and birth-assigned sex at each point in time was found to drop significantly, from -0.88 at 0 months to -0.98 at 6 months and -1.05 at 12 months. Additionally, their standard deviation score for lean mass compared to a male reference population dropped significantly over that time, from -0.68 at 0 months to -1.11 at 12 months. This is noted to reflect the pattern seen among cis women, who have a greater percentage of body fat than cis men. The authors note:

In the transgirls, there was a significant decrease in height and lean mass SDSs over the 12-month period indicating that these birth-assigned males were not maintaining the expected height and lean mass increase over that 1-year period. This significant decrease is likely explained by the fact that these patients are suspended at the same point of puberty as when they started treatment whereas reference data tend to demonstrate an increase in these parameters as age advances. . . . The slowing in height and lean mass accretion may reflect a desirable outcome for transgirls who wish to proceed to a full female sex change and these results have also been reported by other studies [16, 17].

Among the 25 trans boys included in the study and treated with GnRH analogues starting at a mean age of 16.6 years, no significant increase or decrease in lean body mass or rate of height gain was observed, and the authors state that this is likely the result of having started GnRH treatment after natal puberty was completed in those assigned female:

Treatment was commenced in the transboys at an age when most would have completed their sexual development (median age of 16.6 years). . . . Hence this study demonstrates the impact of GnRH analogue post-pubertally which possibly explains why we observed no significant changes in our transboys.

As reduction in final adult height to be closer to that typical of cis women is often a clinical goal in transition treatment for adolescent trans girls, this latest study demonstrates that GnRH analogues can have beneficial effects on height and body composition for trans girls even after they’ve already reached the later stages of their natal puberty.

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About Zinnia Jones

My work focuses on insights to be found across transgender sociology, public health, psychiatry, history of medicine, cognitive science, the social processes of science, transgender feminism, and human rights, taking an analytic approach that intersects these many perspectives and is guided by the lived experiences of transgender people. I live in Orlando with my family, and work mainly in technical writing.
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