A comparison of the urinary excretion of bone resorptive products in white and black children.

Bone density is greater in blacks than in whites regardless of age. In adults, bone formation was shown previously to be much lower in blacks than in whites. A lower bone turnover in adult blacks may preserve a high bone density acquired earlier in life. Whether there is a difference in bone turnover in blacks and whites early in life is not known. Bone resorption is known to parallel bone formation, and thus in the present study we looked for racial differences in bone turnover in children by measuring the nocturnal urinary excretion of three markers of bone resorption: hydroxyproline and the pyridinium cross-links, pyridinoline and deoxypyridinoline. Sixty-four black and 145 white children ages 6 through 15 years were studied. We found excretion of hydroxyproline to be similar in whites and blacks. Urinary excretion of the cross-links was about 10% to 15% lower in blacks, but only the excretion of pyridinoline in boys was significantly lower in blacks (p = 0.031). Overnight urinary calcium excretion was about 30% lower in blacks than in whites (p = 0.0016 for boys and p = 0.008 for girls), as has been reported previously by others. In summary, the excretion rates of bone resorptive products in white and black children were similar, suggesting nearly equal bone turnover in the two racial groups, a finding that contrasts with observations made previously in adults.