Tight Regulation of Circulating 1α,25-Dihydroxyvitamin D in Black Children

To the Editor: We have demonstrated previously that, after challenge with vitamin D, circulating 1α,25-dihydroxyvitamin D is loosely regulated in normal white children and tightly regulated in normal white adults.^1,2 Thus, whereas mean serum 25-hydroxyvitamin D and mean serum 1α,25-dihydroxyvitamin D increased significantly in the white children, mean serum 25-hydroxyvitamin D increased significantly and mean serum 1α,25-dihydroxyvitamin D did not change in the white adults, in response to vitamin D. In the light of these results, we conducted studies to determine the effects of vitamin D in normal black children. Thirteen white children — seven boys and six girls.