NEW YORK (Reuters Health) – Gender-affirming hormone treatment (HT) does not weaken bones in adults with long-term use, according to a new study in hundreds of transgender men and women.

"Hormonal treatment in adult transgender people does not have negative effects on bone mineral density (BMD), at least not during the first ten years of hormonal treatment (BMD), at least not during the first ten years of hormonal treatment," Dr. Chantal Wiepjes of VU University Medical Center in Amsterdam told Reuters Health by email.

HT and Bone Health

Evidence on gender-affirming HT and bone health is mixed, Dr. Wiepjes and her team write in their December 7 report in the Journal of Bone and Mineral Research. In the new study, they followed up on BMD in adults who had received HT at their center in 1998-2018, including 711 transwomen and 543 transmen.

Before starting HT, 21.9% of transwomen and 4.3% of transmen had low BMD. At ten years, both groups had no change in lumbar spine BMD, but lumbar spine Z-score increased by 0.22 in transwomen and by 0.34 in transmen.

"In the previous treatment protocol of our medical center, we used to assess BMD before the start of HT and after that every five years," Dr. Wiepjes said. "However, based on the results of this current study, we evaluated our protocol, and we stopped with regularly assessing BMD."

She noted that the Endocrine Society recommends only measuring BMD in patients with risk factors for osteoporosis, "and especially in those who stop hormonal treatment after gonadectomy."

The researcher added: "It is important to understand that we only studied adult transgender people in this study. Adolescent transgender people can start treatment with puberty suppression, which can also influence bone-mineral density, but these people were not included in our study. Therefore the conclusion of this study is only applicable to adult transgender people."

In this study, we found that transwomen had a low mean LS Z?score before the start of HT, whereas this was not seen in transmen. During the first ten years of HT, no change in LS BMD was observed, whereas the LS Z?score increased in both transwomen and transmen.

Higher estradiol concentrations were associated with an increase in LS BMD in transwomen, whereas in transmen lower LH concentrations were associated with an increase in LS BMD.

Van Caenegem and colleagues earlier described a low bone density in transwomen before the start of HT,26 who found that transwomen had lower 25(OH)D concentrations and lower muscle mass than control men, possibly due to fewer activities because of social isolation. Although we did not have a control group, we did find that transwomen had lower 25(OH)D concentrations at baseline than transmen.