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Accepted 26 October 1996
OBJECTIVES—Despite improved nutrition and
intensive treatment, subjects 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 status. The aim of this study was to determine the relation between circulating concentrations of these peptides, body
mass index, and clinical 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 assessed by Shwachman score and forced expiratory volume in one second (FEV1 ).
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 mass index SD score declined with increasing age (r=−0.18) and paralleled changes in IGF-I concentrations, which also declined. The IGF-I SD score (calculated from control data) correlated with age (r=−0.53). The abnormalities were most obvious during late puberty, when IGF-I and IGFBP3 concentrations were significantly reduced compared with those in control subjects matched for pubertal stage. The IGF-I SD score correlated with height SD score (r=0.14) and the decline in IGF-I concentrations with the fall in body mass index SD score (r=0.42). IGF-I SD scores also correlated with the Shwachman score (r=0.33) and FEV1 (r=0.17).
CONCLUSIONS—The close relation between declining IGF-I and IGFBP3 concentrations and body mass index in patients with cystic fibrosis may simply reflect poor nutritional status and insulin hyposecretion. Nevertheless, IGF-I deficiency could also contribute towards the catabolism observed in these patients, and IGF-I SD scores correlated with other measures of clinical status such as the Shwachman score and FEV1.
• The fall in body mass index with increasing age in children with cystic fibrosis parallels the decline in concentrations of IGF-I and its principal binding protein, IGFB3
• The close relation between body mass index and IGF-I concentrations in cystic fibrosis may reflect poor nutrition or insulin hyposecretion
• Nevertheless, low IGF-I concentrations may contribute directly to the fall in body mass index with increasing age