Gender-affirming hormonal treatment decreases bone turnover in trans women and older trans men

Sex steroids play a key role in bone turnover and preserving BMD. Gender-affirming hormonal treatment (HT) in transgender people affects bone metabolism. Most studies looked into the effect of HT on changes in BMD, however this does not provide insights of changes in bone metabolism due to HT. This study investigated changes in bone turnover markers (BTMs), sclerostin and correlations with change in BMD in trans women and trans men during the first year of HT. Trans women received estradiol and anti-androgens, while trans men received testosterone. Sclerostin, P1NP, alkaline phosphatase (ALP), CTx, and BMD of total hip (TH), femoral neck (FN), and lumbar spine (LS) were evaluated at baseline and after 1 year of HT. 121 Trans women (median age 30 years, IQR 24-41) and 132 trans men (median age 24 years, IQR 21-33) were included. In trans women, ALP decreased with 19% (95%CI -21;-16), CTx with 11% (95%CI -18;-4) and sclerostin with 8% (95%CI -13;-4) after 1 year of HT. In contrast, in trans men P1NP, ALP, and sclerostin increased with 33% (95%CI 24;42), 16% (95%CI 12;20), and 15% (95%CI 10;20), respectively after 1 year of HT. No age differences were seen in trans women, whereas in trans men aged ≥50 years a decrease in all BTMs was found in contrast to the other age groups. These trans men had low estrogen concentration at start of HT, due to their postmenopausal state before start of HT, and estradiol concentrations increased during testosterone treatment. Changes in BTMs and BMD were weakly correlated (correlation coefficient all <0.30). To conclude, 1 year of HT resulted in decreased bone turnover in trans women and older trans men, while it increased in younger trans men. Especially the decrease in bone resorption in the older trans men displays the importance of estrogen as key regulator of bone turnover. This article is protected by copyright. All rights reserved.