Session: MON 586-595-Reproductive Axis Determination, Development & Transgender Medicine
Poster Board MON-591
Gender differences in bone are well described and related to sex steroid hormones. The effect of mechanical stimuli (e.g. muscle mass) is also important for bone acquisition and maintenance. In this study, we examine the bone, muscle and fat mass and bone geometry of transsexual persons undergoing drastic sex steroid changes, during the first year of hormonal therapy.
This research is part of a prospective intervention study conducted in several European gender teams (Ghent, Oslo, Amsterdam, Florence).
We present the data of Ghent gender team with 56 male-to-female (transwomen) of whom 36 have been in follow-up for 1 year of cross-sex hormonal therapy (CSH).
Standardized treatment regimens were used with estradiolvalerate, 4mg daily (or transdermal 100µg/3days for patients older than 45 years old) combined with cyproterone acetate 50mg daily for transwomen. Grip strength (hand dynamometer), areal bone mineral density (aBMD) and total body fat and lean mass using bone densitometry (DXA), bone geometry and volumetric bone mineral density (vBMD), and regional muscle mass and subcutaneous fat mass at the forearm and calf using peripheral quantitative computed tomography, were measured, before the start and after one year of CSH.
Anti-androgens and estrogens induced a loss of total and regional muscle mass (-4 to -10% or – median 2kg) and muscle strength (-7.3%) (all p≤0.001) in transwomen. Furthermore total body fat (+25% or median +4kg) and subcutaneous fat mass (+32% at the calf, +58% at the forearm) increased and a lower waist-hip ratio was found (all p≤0.001).
The aBMD increased at different sites (whole body, lumbar spine and femoral neck; respectively +1%, +4.3%, +1.6%; all p≤0.003) as well as the bone mass (whole body and lumbar spine; both p<0.001). No significant changes were observed in trabecular or cortical bone mass, nor in cortical bone size. The changes in muscle strength correlated inversely with the changes in cortical vBMD (r=-0.374, p=0.027) and positively with bone size (periosteal r=0.385 and endosteal circumference r=0.408, both p≤0.022) at the tibia.
Estrogens and anti-androgens in transwomen lead to an increase in bone mass and fat mass. Next to changes in the sex steroids, the influence of muscle mass on bone size remains important.
Nothing to Disclose: EV, KW, YT, JMK, TS, GGT
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