Henoch-Schönlein purpura (HSP) is a common systemic vasculitis of childhood, and may the kidney. Endothelial cell dysfunction and fibrosis is an important part of HSP vasculitis and may account for renal involvement in HSP. Insulin-like growth factor (IGF)-1 enhances the cytokine-induced expression of adhesion molecules in endothelial cells (EC). Besides, IGF-1 may stimulate angiogenesis, fibrosis and tubular formation in EC and IGF-1 increases glomerular filtration rate. We, therefore, investigated the role of IGF-1 and IGF-binding protein-3 (IGFBP-3) in HSP. The study included 44 patients with HSP (30 boys and 14 girls), including 13 patients with proteinuria, 15 patients with hematuria and 16 patients with positive stool occult blood (SOB), and 26 healthy children. Serum levels of IGF-1 and IGFBP-3 levels were significantly higher in HSP than in the controls (147.9 ± 121.6 vs 95.7 ± 67.8 ng/ml, p = 0.024 and 4.4 ± 2.2 vs 2.3 ± 0.9 μg/ml, p = 0.001, respectively). Serum IGF-1 levels were significantly higher in HSP with proteinuria than those without proteinuria and controls (p = 0.001 and p = 0.001, respectively). Also, IGFBP-3 levels were greater in HSP with proteinuria compared to those without proteinuria and controls (p = 0.005 and p = 0.0001). Serum immunoglobulin-A/complement-C3 ratio was higher in HSP than in the controls (p = 0.0001) but this ratio did not change according to proteinuria, hematuria or positive SOB. In conclusion, IGF-1 and IGFBP-3 levels could be new markers for determination of renal involvement in HSP. © 2008 Tohoku University Medical Press.