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Cross-sex HT induces sex-specific changes in android, gynoid regions

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December 5, 2017

Transgender women and men initiating cross-sex hormone therapy experienced anthropomorphic changes over 1 year associated with more feminine and masculine body fat distributions, respectively, with baseline BMI influencing the extent of any changes, according to findings published in European Journal of Endocrinology.

Maartje Klaver, MD, of the Center of Expertise on Gender Dysphoria at VU University Medical Center in Amsterdam, and colleagues analyzed data from 179 transgender women and 162 transgender men who initiated cross-sex HT between 2010 and April 2016 and were participating in the European Network for the Investigation of Gender Incongruence. Transgender women were treated with 50 mg daily cyproterone acetate combined with 4 mg daily oral estradiol valerate or a 100 µg per 24-hour transdermal estradiol patch twice weekly. Transgender men received 50 mg daily testosterone gel, testosterone undecanoate 1,000 mg intramuscular injection once per 12 weeks or 250 mg testosterone esters once per 2 weeks. Patients visited an outpatient clinic every 3 months during the first year of HT and underwent whole-body DXA scanning, along with standard anthropometric measurements, at baseline and 1 year after HT.

The cohort was followed for a mean of 377 days.

In transgender women, researchers observed increases in body fat that ranged from a mean 18% (95% CI, 13-23) in the android region to a mean 42% (95% CI, 37-46) in the leg region and a mean 34% (95% CI, 29-38) in the gynoid region.

In transgender men, researchers observed decreases in body fat that ranged from a mean 16% (95% CI, –19 to –14) in the leg region and a mean decrease of 14% in the gynoid region (95% CI, –16 to –12). There was no change observed in the android region for transgender men.

Researchers also found that waist-to-hip ratio decreased in transgender women by a mean of –0.03, mainly due to a mean 3.2-cm increase in hip circumference. Transgender men, however, saw a mean 1.9-cm decrease in hip circumference, which accounted for a mean increase in waist-to-hip ratio of 1.

Transgender women with a higher baseline BMI tended to experience smaller increases in body fat and larger decreases in lean body mass, according to researchers; however, for transgender men, a higher baseline BMI was associated with a larger decrease in body fat and a smaller increase in lean body mass. Age at initiation of therapy was not related to body changes after adjustment for baseline BMI; the use of other medications, including antidepressants and corticosteroids, was also not associated with changes in body measurements, according to researchers. Additionally, type of hormonal therapy or the concentration of estradiol did not affect changes in regional body fat or lean body mass in transgender women; however, transgender men using T esters seemed to experience larger changes in body composition than transgender men using T gel.

“This study provides insight into the effects of cross-sex hormonal therapy on body shape and body composition,” Klaver told Endocrine Today. “Transgender persons starting treatment can now be better informed on the extent to which their bodies will change and on what to expect of the results of treatment. Further, this study showed that higher serum estradiol levels did not result in larger changes in body fat and lean body mass. This is a relevant finding, since in clinical practice, many transwomen wonder whether they would experience larger effects if their hormone dosage would be increased.”

The researchers said future research should focus on whether such changes are also reflected in a changing physical appearance — for example, whether an increase in body fat and decrease in lean body mass in transgender women causes the arm “to look more feminine and to feel softer.” – by Regina Schaffer

For more information:

Maartje Klaver, MD, can be reached at the Center of Expertise on Gender Dysphoria at VU University Medical Center, De Boelelaan 1118, 1081 HZ, Amsterdam; email: ma.klaver2@vumc.nl.

Disclosures: The authors report no relevant financial disclosures.

itj+ Perspective

Guy T'Sjoen
Perspective

Persons with gender dysphoria can be treated with gender-affirming hormones with a goal to obtain physical characteristics of the desired sex, aiming at a more feminine or masculine body shape, body fat distribution or musculature. We experience in clinical care that some transgender persons’ expectations may be very high about the effects of hormone treatment on body shape, and some wish for a rapid virilization or feminization.

Reassuringly, Klaver and colleagues reported that, as measured by DXA and evaluating separate body regions, 1 year of hormone treatment showed a more feminine body fat distribution in transgender women, with a greater increase in body fat in the gynoid region vs. the android region. The waist-to-hip ratio of transgender women decreased due to an increase in hip circumference. Neither the HT regimen used to achieve feminization nor the concentration of estradiol affected changes in regional body fat. A more masculine body fat distribution in transgender men is being reported, including a smaller hip circumference; they saw a decrease in percentage body fat in the gynoid region with no change in the android region. Transgender men using intramuscular testosterone esters seemed to experience larger changes in body composition, compared with those participants using testosterone gel. The study also found that transgender women and transgender men with BMI at least 20 kg/m2 experienced larger changes in all body fat measures and body fat in the android region, respectively, compared with normal weight, overweight and obese participants.

The study population of 341 participants is larger than any previous study on the relation of gender-affirming hormonal treatment and the effects on body composition and shape.

The findings come from the ENIGI (European Network for the Investigation of Gender Incongruence) study, a collaboration of several European gender-identity clinics, using the same diagnostic and psychological assessment battery and a common hormone treatment protocol. The prospective study currently includes 1,600 participants before initiation of hormonal therapy and onwards.

The group’s newest published paper shows 1-year changes in body composition upon start of hormone treatment, underlining virilization and feminization do occur as desired; however, changes take time to develop. Based upon the absent associations with estradiol concentrations, increasing hormone dosage in transgender women is unlikely to yield better effects, whereas there is a suggestion that testosterone esters induce larger changes than testosterone gel, possibly due to higher serum testosterone levels.

Guy T’Sjoen, MD, PhD

Department of Endocrinology and Center for Sexology and Gender
Ghent University Hospital
Belgium

Disclosure: T’Sjoen reports he is principal investigator for the ENIGI study.