Effects of growth hormone on growth factors after renal transplantation

Abstract 

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.