Serum 1,25-dihydroxyvitamin D levels in normal children and in vitamin D disorders.

Using a precise assay for 1,25-dihydroxyvitamin D in serum, the levels in 103 children, aged 13 months to 16 years, were found to be 43 +/- 2 pg/mL (mean +/- SE). This value is higher than reported values in adults and in neonates. Age-related changes in 1,25-dihydroxyvitamin D levels during childhood were also evident. Older children have significantly higher levels than children less than 11 years, possibly indicating changes with puberty and the adolescent growth spurt. The values were significantly reduced in childhood uremia (13 +/- 5 pg/mL), in hypoparathyroidism (16 +/- 1 pg/mL), and in children with Fanconi's syndrome. Treatment with oral calcitriol in these three groups of patients led to increased serum levels.