Hormone therapy and puberty blockers alter skeletal size in transgender individuals

Skeletal size may be altered by gender-affirming hormone therapy only if puberty has also been suppressed during adolescence, according to research presented at the 62nd Annual European Society for Paediatric Endocrinology Meeting in Liverpool. The findings from this research, carried out by Amsterdam UMC, not only help researchers further understand the roles sex hormones play on the skeleton but may also improve counselling on gender-affirming treatment in transgender individuals.

Skeletons of men and women vary in size and proportion. For instance, men typically have broader shoulders while women have a wider pelvis. Gender-affirming hormones are used to better align an individual's physical appearance with their gender identity. What's more, puberty blockers (gonadotrophin-releasing hormone analogues) can be used to delay or prevent the changes associated with puberty in transgender youth. However, how sex hormones affect the skeleton such as the shoulders and pelvis of transgender individuals is still unclear.

To investigate this, researchers from the Amsterdam University Medical Center (UMC) in the Netherlands analysed data on the shoulder and pelvis dimensions of 121 transgender women and 122 transgender men who were either undergoing gender-affirming hormone therapy – with or without previously taking puberty blockers – or had not taken any therapy. The researchers found that only transgender men who had been treated with puberty blockers from early puberty, followed by hormone therapy, had broader shoulders and a smaller pelvic inlet (upper opening of the pelvis) compared to untreated individuals, while transgender women had smaller shoulders only after treatment from early puberty. In addition, transgender women under treatment had a larger pelvis, but this change was most noticeable in those who started blocking puberty earlier.

"To our knowledge, this is the first study to explore the effect of both gender-affirming hormones and puberty blockers on the pelvic dimensions," said Ms. Lidewij Boogers, a PhD student at Amsterdam UMC who led the study. "Shoulder width is only affected when puberty suppression is initiated in early puberty, while pelvic dimensions may be sensitive to hormonal changes even after puberty has ended."

Since skeletal dimensions from individuals who started puberty suppression in early puberty were most similar to those of the affirmed gender, our findings suggest that irreversible skeletal changes occur during puberty."

Ms. Lidewij Boogers, PhD student, Amsterdam UMC

The researchers will next assess the extent to which physical changes that occur during puberty suppression and gender-affirming hormones impact body image and quality of life in transgender adolescents. "We are currently conducting a prospective study, with the collected data we aim to further evaluate the relation between physical changes and psychological outcomes in this population. This could help optimize treatment and improve counselling for individuals who seek treatment," said Ms Boogers.