RELATION BETWEEN INSULIN-LIKE GROWTH-FACTOR-I, BODY-MASS INDEX, AND CLINICAL STATUS IN CYSTIC-FIBROSIS

Objectives-Despite improved nutrition and intensive treatment, subject s with cystic fibrosis have difficulty in maintaining anabolism during intercurrent infections, which can result in reduced body mass index and impaired skeletal growth. Insulin-like growth factor-I (IGF-I) and its binding protein IGFBP3 are sensitive to changes in nutritional st atus. The aim of this study was to determine the relation between circ ulating concentrations of these peptides, body mass index, and clinica l status in cystic fibrosis. Methods-Serum concentrations of IGF-I and IGFBP3 were measured in 197 subjects (108 males, 89 females; mean age 9.69 years, range 0.41-17.9 years) and these data were analysed with respect to body mass index, pubertal stage, and clinical status as ass essed by Shwachman score and forced expiratory volume in one second (F EV1). Results-The mean height SD score of the children studied was -0. 2 (SD 1.14) and the body mass index SD score -0.26 (1.4). The body mas s index SD score declined with increasing age (r=-0.18) and paralleled changes in IGF-I concentrations, which also declined. The IGF-I SD sc ore (calculated from control data) correlated with age (r=-0.53). The abnormalities were most obvious during late puberty, when IGF-I and IG FBP3 concentrations were significantly reduced compared with those in control subjects matched for pubertal stage. The IGF-I SD score correl ated with height SD score (r=0.14) and the decline in IGF-I concentrat ions with the fall in body mass index SD score (r=0.42). IGF-I SD scor es also correlated with the Shwachman score (r=0.33) and FEV1 (r=0.17) . Conclusions-The close relation between declining IGF-I and IGFBP3 co ncentrations and body mass index in patients with cystic fibrosis may simply reflect poor nutritional status and insulin hyposecretion. Neve rtheless, IGF-I deficiency could also contribute towards the catabolis m observed in these patients, and IGF-I SD scores correlated with othe r measures of clinical status such as the Shwachman score and FEV1.