Serum concentrations of 24,25(OH)2D in uremic children: a reflection of renal function

The mean serum concentration of 24,25(OH)2D determined by competitive protein-binding radioassay was significantly lower in ten uremic children maintained on hemodialysis (0.82 +/- 0.43[SD] ng/ml) than in ten patients with impaired renal function not requiring hemodialysis (1.30 +/- 0.54 ng/ml, P less than 0.05), or in 12 normal children (2.98 +/- 1.57 ng/ml, P less than 0.01). The serum levels of 250HD were similar in all groups. There were significant (P less than 0.01) positive correlations between the serum concentration of 24,25(OH)2D or the ratio 24,25(OH)2D/25OHD and the creatinine clearance. The serum concentration of 24,25(OH)2D was significantly decreased also in six anephric adults relative to normal adult values. The data indicate that production of 24,25(OH)2D is impaired in subjects with compromised renal function. Inasmuch as the major active metabolite of Vitamin D, i.e., 1,25(OH)2D, is requried for renal synthesis of 24,25(OH)2D measurement of the latter metabolite may provide a convenient method for assessment of renal vitamin D metabolism. The role of this metabolite in the pathogenesis of renal osteodystrophy remains speculative.