Growth retardation occurs frequently in renal transplanted children (RTx) and can be improved by growth hormone (GH) treatment. This study retrospectively examines the insulin-like growth factor-1 (IGF-1) and IGF binding protein (IGFBP) profile of ten growth-retarded children previously given renal allografts, after 1 year of GH treatment period. Ten prepubertal patients (nine boys and one girl) were investigated. They had a mean chronological age (CA) of 11.4 +/- 1.1 years and a mean bone age (BA) of 7.3 +/- 0.9 years. Mean height was -3.9 +/- 0.4 SD units below the mean for CA. The mean body mass index (BMI) was 16.9 +/- 0.6 and the mean inulin clearance was 36.5 +/- 4.9 ml/min/1.73 m2. Recombinant hGH was given at 4 IU/m2/day. Plasma GH, total and free IGF-1, IGFBP-2 and -3 were measured by specific radioimmunoassay (RIA). IGFBPs were characterized by SDS PAGE techniques and ligand and immunoblot analyses. Mean velocity was markedly increased (P < 0.01) after 1 year of GH therapy, expressed as SD score for BA. The range of growth response was wide. The total and free plasma IGF-1 increased (P < 0.01) by about 100% (mean values after GH therapy: 95.9 +/- 2.1 nM and 165 +/- 29 pM, respectively). Plasma IGFBP-3 concentrations increased by about 40% (mean value: 148 +/- 18 pM, P < 0.01), with a concomitant increase in both intact IGFBP-3 and its 30-kDa proteolytic fragment. There was no change in plasma IGFBP-2 concentration. Both mean values of inulin clearance and BMI were unchanged during the treatment. In view of the IGF-1/IGFBP concentration changes, there should have been an even better growth response to GH therapy in these patients. This strongly suggests IGF-1 insensitivity, probably as a result of corticosteroid therapy.