Evaluation of vitamin D-binding protein and vitamin D metabolite loss in children on continuous ambulatory peritoneal dialysis.

We measured the serum concentration of vitamin D-binding protein (DBP) in children with chronic renal failure (CRF). We also evaluated the relationships between the peritoneal loss of vitamin D metabolites, DBP and albumin in nine children on continuous ambulatory peritoneal dialysis (CAPD). The serum levels of DBP in children with CRF were significantly higher than in normal children. The mean serum DBP level in CRF children undergoing CAPD was slightly lower than in CRF patients who were not on dialysis. In patients on CAPD, the peritoneal loss of 25-hydroxyvitamin D (25OHD) showed a significant positive correlation with the DBP concentration in the dialysate (r = 0.855, P less than 0.005). In contrast, the peritoneal loss of 1,25-dihydroxyvitamin D (1,25(OH)2D) showed a significant correlation with the loss of albumin in the dialysate (r = 0.779, P less than 0.01). The synthesis of 1,25(OH)2D3 is reduced in advanced renal failure, and the peritoneal losses of the active vitamin D sterols in patients on CAPD may aggravate this deficiency. We recommend that supplementation of active form of vitamin D, such as 1 alpha-hydroxyvitamin D3 or 1,25(OH)2D3, is important in CAPD patients, particularly those with elevated peritoneal loss of DBP and/or albumin.