Variation in sensitivity and rate of change in body composition: steps toward individualizing transgender care

Abstract

Objective Transgender individuals sometimes report a lack of physical change during hormone treatment, such as alterations in muscle tone or fat distribution. Identifying characteristics of this subgroup could be a step towards individualizing hormone therapy in transgender individuals. Therefore, we study the variation of changes in body composition and characteristics associated with a lack of change. Design and methods: Body composition measures were recorded in 323 transmen and 288 transwomen at every visit from start of hormone therapy to a maximum of 24 months follow-up. Absence of change was defined as transmen with a decrease in lean body mass or transwomen with a decrease in fat percentage. Results A lack of change at 24 months was observed in 19 of 94 (20.2%) transmen and in 9 of 96 (9.4%) transwomen. The risk of not achieving change in body composition was related to lower testosterone levels and less suppression of LH in transmen (OR 0.67, 95% CI: 0.48-0.94 per SD increase in testosterone and OR 1.36, 95% CI 1.01-1.83 per SD increase in LH). Conclusion There is a large variation in body composition changes during hormone therapy, with a substantial proportion of individuals with no measurable effects. In transmen, serum testosterone and LH were associated with a lack of change, but serum hormone levels were not associated with body composition changes in transwomen. The results provide a rationale for individualizing hormone therapy in transmen, by considering individuals effects rather than solely relying on a standardized dosages of hormone therapy.

The Role of Estrone in Feminizing Hormone Treatment

“…Estradiol concentrations were also not associated with these outcomes. This is in line with previous studies in trans women, which found no association between estradiol concentrations or administration route and change in fat percentage or breast development ( 3 , 19 , 34 ). Our results are in contrast with other studies suggesting that high estrone levels can act as an estrogen antagonist ( 14 , 35-37 ).…”

“…The machine output of fat percentages was used. A more detailed description of the bioelectrical impedance analysis protocol is described elsewhere ( 3 ).…”

“…Previous studies have focused on differences in administration route of estradiol, estradiol concentrations, types of antiandrogens, and lifestyle. However, none of these factors seems to explain the difference in amount of feminization ( 3 , 4 ).…”

Gender‐affirming hormone therapy: An updated literature review with an eye on the future

“…However, body composition did change, fat percentage decreased (−4%) and lean mass increased (+1.6%), also resulting in increased handgrip strength [61]. A lack of changes with GAHT in body composition was examined in ENIGI [62]; in 323 trans men (mean age = 21), a lack of change after 24 months of GAHT was observed in 20.2%. Low mean testosterone and high mean luteinizing hormone (LH) levels were associated with no change in this group.…”

The ENIGI (European Network for the Investigation of Gender Incongruence) Study: Overview of Acquired Endocrine Knowledge and Future Perspectives

“…Body mass index (BMI) appeared to be an important determinant of body composition changes, with lower BMI associated with greater modifications [ 10 ]. Furthermore, in trans AFAB people, lower T and higher luteinizing hormone levels showed an association with a lack of body composition changes [ 11 ].…”