Hormonal and biochemical determinants of trabecular microstructure at the ultradistal radius in women and men

Context: Using high-resolution three-dimensional peripheral quantitative computed tomography (3D-pQCT) imaging, we recently described sex and age effects on bone microstructure at the ultradistal radius in men and women. Although bone volume/tissue volume decreased with age in both sexes, changes in trabecular number (TbN) and thickness (TbTh) in men were complex, with evidence for conversion of thick trabeculae into more numerous, thinner trabeculae in young men. Objective: Our objective was to define the relationship between hormonal and bone turnover variables and trabecular microstructure at the ultradistal radius. Design, Setting, and Participants: We conducted a population-based, cross-sectional study in the general community that included 205 women and 269 men, aged 21-97 yr. Main Outcome Measures: We measured correlation of bone volume/tissue volume, TbN, TbTh, and trabecular separation with hormonal and bone turnover variables. Results: In young men (20-39 yr), TbTh and TbN were associated with serum IGF-I levels (r=0.31, P<0.05 and r=-0.35, P<0.01, respectively). No associations were found between sex steroid levels (bioavailable estradiol or testosterone) or biochemical markers of bone turnover and trabecular parameters in young men or women. By contrast, in elderly men and women (>60 yr), sex steroids were the most consistently associated with trabecular microstructure, and bone turnover markers were variably associated with these parameters. Conclusions: In young men, the apparent conversion of thick trabeculae into more numerous, thinner trabeculae is most closely associated with declining IGF-I levels. By contrast, sex steroids are the major hormonal determinants of trabecular microstructure in elderly men and women.