Comparison of Metabolism of Vitamins D2 and D3 in Children With Nutritional Rickets

Children with calcium-deficiency rickets may have increased vitamin D requirements and respond differently to vitamin D-2 and vitamin D-3. Our objective was to compare the metabolism of vitamins D-2 and D-3 in rachitic and control children. We administered an oral single dose of vitamin D-2 or D-3 of 1.25 mg to 49 Nigerian children-28 with active rickets and 21 healthy controls. The primary outcome measure was the incremental change in vitamin D metabolites. Baseline serum 25-hydroxyvitamin D [25(OH)D] concentrations ranged from 7 to 24 and 15 to 34 ng/mL in rachitic and control children, respectively (p < .001), whereas baseline 1,25-dihydroxyvitamin D [1,25(OH)(2)D] values (mean +/- SD) were 224 +/- 72 and 121 +/- 34 pg/mL, respectively (p < .001), and baseline 24,25-dihydroxyvitamin D [24,25(OH)(2)D] values were 1.13 +/- 0.59 and 4.03 +/- 1.33 ng/mL, respectively (p < .001). The peak increment in 25(OH)D was on day 3 and was similar with vitamins D-2 and D-3 in children with rickets (29 +/- 17 and 25 +/- 11 ng/mL, respectively) and in control children (33 +/- 13 and 31 +/- 16 ng/mL, respectively). 1,25(OH)(2)D rose significantly (p < .001) and similarly (p=.18) on day 3 by 166 +/- 80 and 209 +/- 83 pg/mL after vitamin D-2 and D-3 administration, respectively, in children with rickets. By contrast, control children had no significant increase in 1,25(OH)(2)D (19 +/- 28 and 16 +/- 38 pg/mL after vitamin D-2 and D-3 administration, respectively). We conclude that in the short term, vitamins D-2 and D-3 similarly increase serum 25(OH)D concentrations in rachitic and healthy children. A marked increase in 1,25(OH)(2)D in response to vitamin D distinguishes children with putative dietary calcium-deficiency rickets from healthy children, consistent with increased vitamin D requirements in children with calcium-deficiency rickets. 0 2010 American Society for Bone and Mineral Research.