[The influence of corticosteroid therapy on selected parameters of bone metabolism in children with nephrotic syndrome].

The aim of the study was to evaluate the influence of prednisone therapy on selected parameters of bone metabolism [carboxyterminal propeptide of type I procollagen (PICP), carboxyterminal pyridinoline crosslinked telopeptide of type I collagen (ICTP), alkaline phosphatase (AP), parathormone (PTH), and calciuria (Cau) in children with nephrotic syndrome. Twenty patients (aged 4-15 years, mean: 9.2 years) were treated with prednisone. Blood and urine samples were taken: T0--before prednisone treatment; T1--after two weeks of treatment with prednisone 1-2 mg/kg/24 h; T2--after two weeks of treatment with prednisone 1-2 mg/kg/48 h; T3--after 3 months of treatment with prednisone; T6--in 6th month of treatment with prednisone, at dose 0.2-0.4 mg/kg/48 h. Mean values of PICP, ICTP, AP concentration, and PICP/ICTP ratio found in the T1 period were significantly lower, and mean Cau value was higher in comparison to means of these parameters observed before steroid treatment. After two weeks of prednisone administered every 48 hours mean values of PICP, ICTP concentrations and PICP/ICTP ratio were significantly higher than in the T1 period of treatment. There were no significant differences in mean concentrations of PTH before and during everyday doses of prednisone therapy. Mean value of PTH concentration decreased significantly during T2 in comparison with T1 period of prednisone treatment. Our data demonstrate that short-term treatment with high daily doses of prednisone in children with nephrotic syndrome is associated with increase of calciuria and suppression of serum markers of type I collagen's turnover. Changes of PICP, ICTP, and PICP/ICTP ratio depend on a method of steroid administration. Decreased PICP/ICTP ratio during daily steroid treatment may indicate stronger inhibition of bone formation than bone resorption, but significance of PICP/ICTP ratio in later phases of treatment needs further studies. Present study suggests that prednisone influences bone metabolism directly rather than by stimulating the parathyroids.