Endocrine Abstracts

Background: Concerns about the effects of gender affirming hormonal treatment (HT) on bone mineral density (BMD) exists, particularly for transmen with decreasing estrogen levels. HT in transpersons affects BMD on short term, but long-term follow-up studies are lacking. Therefore this study aimed to investigate the change in BMD during the first 10 years of HT in adult transwomen and transmen, in order to determine whether it is necessary to assess BMD during HT.

Methods: A retrospective cohort study was performed in adult transpersons receiving HT at the VU University medical center Amsterdam (the Netherlands) between 1998 and 2015. Persons were included for analyses if they were gender affirming hormone naïve and had a dual-energy X-ray absorptiometry (DXA) scan at the start of HT. Follow-up DXA scans performed after 2, 5, or 10 years of treatment were used for analyses. The course of Z-scores of the lumbar spine during the first ten years of HT were analyzed using multilevel analysis, and the influence of age and serum sex hormone levels during HT were analyzed.

Results: Seven hundred and eleven transwomen (age 35 years, IQR 26–46) and 543 transmen (age 25 years, IQR 21–34) were included for analyses. Prior to the start of HT, 21.9% of transwomen and 4.2% of transmen had a low bone density, defined as a Z-score below −2.0. In transwomen, mean baseline Z-score was −0.93 (S.D.±1.32), which increased with +0.22 (95%CI 0.12 – 0.32) after ten years of HT. Transmen had a mean baseline Z-score of 0.01 (S.D.±1.14), which increased with +0.34 (95%CI 0.23 – 0.45) after ten years of HT. In both transwomen and transmen, Z-score increased more in the oldest age group (>40 years) compared with the younger age groups. In transwomen, higher estradiol level gave a higher increase in Z-score, while in transmen lower LH levels gave a higher increase in Z-score. Testosterone levels were not correlated with change in Z-score.

Conclusion: This study showed that HT does not have negative effects on BMD in transgender persons, which makes regularly assessment of BMD during HT not necessary. Higher estradiol levels in transwomen and lower LH levels in transmen gave a larger increase in Z-score, which indicates that adequate hormone substitution and therapy compliance should be stimulated. However, as even prior to HT a high percentage of low BMD is found, bone health remains an important health topic in transpersons.