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. © 2010 American Society for Bone and
Mineral Research.