Preservation of volumetric bone density and geometry in trans women during cross-sex hormonal therapy: a prospective observational study.
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.


OBJECTIVE
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.


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
Department of Endocrinology, Ghent University Hospital, De Pintelaan 185, 9000, Ghent, Belgium, eva.vancaenegem@ugent.be.
E
E
Van Caenegem
K
K
Wierckx
Y
Y
Taes
T
T
Schreiner
S
S
Vandewalle
K
K
Toye
J-M
JM
Kaufman
G
G
T'Sjoen
D015502:Absorptiometry, Photon / Q000379:methods; D000328:Adult; D001823:Body Composition; D015519:Bone Density / Q000187:drug effects* / Q000502:physiology; D016723:Bone Remodeling / Q000187:drug effects; D016022:Case-Control Studies; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D020738:Leptin / Q000097:blood; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D053580:Muscle Strength / Q000187:drug effects; D018482:Muscle, Skeletal / Q000473:pathology; D011446:Prospective Studies; D057829:Gender-Affirming Procedures / Q000379:methods*; D014189:Transsexualism / Q000097:blood / Q000503:physiopathology*; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
D020738:Leptin; D014807:Vitamin D; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; C104450:25-hydroxyvitamin D