Levine, Michael A.

Abstract Children with calcium-deficiency rickets may have increased vitamin D requirements and respond differently to vitamin D2 and vitamin D3. Our objective was to compare the metabolism of vitamins D2 and D3 in rachitic and control children. We administered an oral single dose of vitamin D2 or D3 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)2D] values (mean ± SD) were 224 ± 72 and 121 ± 34 pg/mL, respectively (p < .001), and baseline 24,25-dihydroxyvitamin D [24,25(OH)2D] 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 D2 and D3 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)2D rose significantly (p < .001) and similarly (p = .18) on day 3 by 166 ± 80 and 209 ± 83 pg/mL after vitamin D2 and D3 administration, respectively, in children with rickets. By contrast, control children had no significant increase in 1,25(OH)2D (19 ± 28 and 16 ± 38 pg/mL after vitamin D2 and D3 administration, respectively). We conclude that in the short term, vitamins D2 and D3 similarly increase serum 25(OH)D concentrations in rachitic and healthy children. A marked increase in 1,25(OH)2D 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

Abstract Oncogenic osteomalacia (OOM) is associated with primitive mesenchymal tumors that secrete phosphaturic factors resulting in low serum concentrations of phosphate and calcitriol, phosphaturia, and defective bone mineralization. To identify overexpressed genes in these tumors, we compared gene expression profiles of tumors resected from patients with OOM and histologically similar control tumors using serial analysis of gene expression (SAGE). Three hundred and sixty-four genes were expressed at least twofold greater in OOM tumors compared with control tumors. A subset of 67 highly expressed genes underwent validation with an extended set of OOM and control tumors using array analysis or reverse-transcription polymerase chain reaction (RT-PCR). Ten of these validated genes were consistently overexpressed in all OOM tumors relative to control tumors. Strikingly, genes with roles in bone matrix formation, mineral ion transport, and bone mineralization were highly expressed in the OOM tumors.