Bone Abstracts

Sex-differences in bone strength manifest at late puberty likely due to sex-specific hormonal stimulus to bone development. Comparisons of bone structural properties between sexes in years preceding the pubertal growth are lacking. Our objective was to assess sex-differences in bone strength, size, density and micro-architecture in childhood. We scanned distal and shaft sites of the radius and tibia from 85 girls and 75 boys (mean age 10.8, S.D. 1.8 years) using peripheral quantitative computed tomography (pQCT) and high resolution pQCT. We defined biological age by calculating age from the estimated age at peak height velocity (aPHV). We included participants with a biological age of 0 to −4 years from aPHV and excluded post-menarcheal girls. We measured and compared (t-tests) anthropometrics, physical activity levels and dietary intakes of protein, calcium and vitamin-D between sexes to identify covariates (for bone outcomes) that differed between sexes. We used MANCOVA (covariates: biological age, height and weight) to compare total, cortical and trabecular bone areas and densities, trabecular micro-architecture (thickness and number) and bone volume fraction, and estimated bone strength against compression at distal sites between girls and boys. We also compared total and cortical areas, cortical density and bone strength against torsion at the shaft sites of the radius and tibia. At the distal sites, girls had 10–19% smaller total, cortical and trabecular area, 7–10% lower total and trabecular density, 4% fewer trabeculae and 20% lower estimated bone strength against compression. At the shaft sites, girls had 20% smaller total area and 12% lower bone strength against torsion at the radius. We did not observe any sex-differences at the tibia shaft. Results suggest that boys have favourable bone size, density, micro-architecture and strength particularly at the distal radius and radius shaft already in childhood. In contrast, tibia bone properties at the shaft did not differ between sexes. These findings suggest that in addition to systemic factors (e.g. hormones) local factors (e.g., mechanical loading) may contribute to sex-specific bone development in childhood. A better understanding of sex-specific development in bone structure, micro-architecture and strength, along with information of modifiable factors, will guide investigations and strategies aiming to optimize primary prevention of osteoporosis and bone fragility, particularly in females.

Disclosure: The authors declared no competing interests.