Preservation of volumetric bone density and geometry in trans women during cross-sex hormonal therapy: a prospective observational study
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Although trans women before the start of hormonal therapy have a less bone and muscle mass compared with control men, their bone mass and geometry are preserved during the first 2 years of hormonal therapy, despite of substantial muscle loss, illustrating the major role of estrogen in the male skeleton.
The aim of this study is to examine the evolution of areal and volumetric bone density, geometry, and turnover in trans women undergoing sex steroid changes, during the first 2 years of hormonal therapy.
In a prospective observational study, we examined 49 trans women (male-to-female) before and after 1 and 2 years of cross-sex hormonal therapy (CSH) in comparison with 49 age-matched control men measuring grip strength (hand dynamometer), areal bone mineral density (aBMD), and total body fat and lean mass using dual X-ray absorptiometry (DXA), bone geometry and volumetric bone mineral density, regional fat, and muscle area at the forearm and calf using peripheral quantitative computed tomography. Standardized treatment regimens were used with oral estradiol valerate, 4 mg daily (or transdermal 17-β estradiol 100 μg/24 h for patients >45 years old), both combined with oral cyproterone acetate 50 mg daily.
Prior to CSH, trans women had lower aBMD at all measured sites (all p < 0.001), smaller cortical bone size (all p < 0.05), and lower muscle mass and strength and lean body mass (all p < 0.05) compared with control men. During CSH, muscle mass and strength decreased and all measures of fat mass increased (all p < 0.001). The aBMD increased at the femoral neck, radius, lumbar spine, and total body; cortical and trabecular bone remained stable and bone turnover markers decreased (all p < 0.05).
Although trans women, before CSH, have a lower aBMD and cortical bone size compared with control men, their skeletal status is well preserved during CSH treatment, despite of substantial muscle loss.
KeywordsBone transsexual gender dyspohria sex steroids prospective
The authors are indebted to Griet De Cuypere, MD, PhD; Gunter Heylens, MD; Els Elaut, MSc, Birgit Van Hoorde, MSc; Steven Weyers, MD, PhD; Piet Hoebeke, MD, PhD; Stan Monstrey, MD, PhD; for referral of participants and to Jens Jacobeit, MD (Endokrinologikum, Hamburg, Germany) and Mick van Trotsenburg, MD (Vrije Universiteit, Amsterdam, the Netherlands) for their contribution to the development of the ENIGI endocrinological protocol. We thank all volunteers who participated as study subjects. We also thank Veronique Van den Bossche and Kathelyne Mertens for their excellent technical assistance. This work was supported in part by Grant G.0867.11 from the Research Foundation Flanders; Eva Van Caenegem, Sara Vandewalle, and Katrien Wierckx are holders of a PhD fellowship respectively from the Research Foundation Flanders (Eva Van Caenegem and Sara Vandewalle) and Ghent University (Katrien Wierckx).
Conflicts of interest
Eva Van Caenegem, Katrien Wierckx, Youri Taes, Thomas Schreiner, Sara Vandewalle, Kaatje Toye, Jean-Marc Kaufman, and Guy T’Sjoen declare that they have no conflict of interest.
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