Difference in Bone Mass between Black and White American Children: Attributable to Body Build, Sex Hormone Levels, or Bone Turnover?

A cross-sectional study of 232 healthy children, with about equal numbers of boys and girls and blacks and whites, aged 4 to 16 yr, was conducted to investigate the racial differences in bone mineral. Bone mineral content (BMC) by dual x-ray absorptiometry was found to be similar between blacks and whites at the spine after controlling for age and Tanner stage. However, total body BMC was higher in blacks, compared with whites of the same age and Tanner stage. Height and weight alone reduced the racial difference in BMC from 152 g to 66 g in girls and from 163 g to 105 g in boys, in whom the difference was further reduced to 66 g after accounting for lean and fat body mass and subscapular skinfold. The only significant sex hormone was androstenedione, which explained another 4-5 g of the racial difference in total body BMC for both boys and girls. Among the biochemical variables, only 25OH vitamin D reduced the residual racial difference in total body BMC to 39 g in girls, whereas serum PTH, urine free deoxypyridinoline ratio, and 1,25(OH)(2) vitamin D reduced the residual difference to 25 g in boys. The residual racial differences in bone mass were not statistically significant.