Context: Using high resolution 3-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. While bone volume/tissue volume (BV/TV) 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: To define the relationship between hormonal and bone turnover variables and trabecular microstructure at the ultradistal radius.

Design: Population-based, cross-sectional study.

Setting: General community.

Participants: 205 women and 269 men, age 21 to 97 yr.

Main Outcome Measures: Correlation of BV/TV, TbN, TbTh and trabecular separation (TbSp) with hormonal and bone turnover variables.

Results: In young men (20-39 yr), TbTh and TbN were associated with serum insulin-like growth factor (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.