Decreased serum 24,25-dihydroxy vitamin D concentrations in children receiving chronic anticonvulsant therapy.

Serum 24,25-dihydroxy vitamin D (24,25(OH)2D) and 25-hydroxy vitamin D (25-OHD) concentrations and the ratio between the two were measured in 31 Israeli children and adolescents receiving long-term treatment with phenobarbitone or phenytoin and in controls. 24,25 (OH)2D concentrations were significantly depressed in the patients, although the 25-OHD concentrations were similar to those in the healthy controls. In four patients with radiological evidence of osteopenia very low serum 24,25(OH)2D concentrations and serum 24,25(OH)2D: 25-OHD ratios were recorded. The findings suggest that 24,25(OH)2D deficiency may play an important part in the pathogenesis of osteomalacia in patients treated with anticonvulsant drugs and provide further indirect evidence that 24,25(OH)2D is important for normal bone structure.