[Levels of plasma 1,25-dihydroxyvitamin D and parameters of phospho-calcium metabolism in children with non-dialyzed chronic renal failure].

1,25-diOH vitamin D, 25-OH vitamin D, parathyroid hormone, calcium and phosphorus were measured in the blood of 34 children and correlated. These children, 3 months to 17 years old, had chronic renal insufficiency of varying intensity. 15 of them were treated with vitamin D. We found a negative correlation between the 1,25-diOHD levels and the reduction of the clearance of inuline, serum creatinine and uremia. This suggests a defect in 1,25-diOHD synthesis appearing when the glomerular filtration rate is decreased by about 50%, except in the case of tubulopathies, where it appears earlier. In these children, the 1,25-diOHD levels correlated with calcemia, but not with phosphoremia. The high levels of PTH were related with the lowest levels of 1,25-diOHD. The regulation of calcemia is thus basically controlled by the renal possibilities. There was a positive correlation between 1,25-diOHD and 25OHD levels when GFR was lower than 0.6 ml/sec./1,73 m2, indicating a dependence of 1,25-diOHD levels or its substrate in severe chronic renal failure.