Relation between insulin-like growth factor-I,body mass index, and clinical status in cystic fibrosis

Accepted 26 October 1996
OBJECTIVES—Despite improved nutrition andintensive treatment, subjects with cystic fibrosis have difficulty inmaintaining anabolism during intercurrent infections, which can resultin reduced body mass index and impaired skeletal growth. Insulin-likegrowth factor-I (IGF-I) and its binding protein IGFBP3 are sensitive tochanges in nutritional status. The aim of this study was to determine the relation between circulating concentrations of these peptides, bodymass index, and clinical status in cystic fibrosis.
METHODS—Serum concentrations of IGF-I and IGFBP3were 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 respectto body mass index, pubertal stage, and clinical status as assessed byShwachman score and forced expiratory volume in one second (FEV₁ ).
RESULTS—The mean height SD score of the childrenstudied 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-Iconcentrations, which also declined. The IGF-I SD score (calculatedfrom control data) correlated with age (r=−0.53). Theabnormalities were most obvious during late puberty, when IGF-I andIGFBP3 concentrations were significantly reduced compared with those incontrol subjects matched for pubertal stage. The IGF-I SD scorecorrelated with height SD score (r=0.14) and the declinein IGF-I concentrations with the fall in body mass index SD score(r=0.42). IGF-I SD scores also correlated with theShwachman score (r=0.33) and FEV₁(r=0.17).
CONCLUSIONS—The close relation between decliningIGF-I and IGFBP3 concentrations and body mass index in patients withcystic fibrosis may simply reflect poor nutritional status and insulinhyposecretion. Nevertheless, IGF-I deficiency could also contributetowards the catabolism observed in these patients, and IGF-I SD scorescorrelated with other measures of clinical status such as the Shwachmanscore and FEV₁.

• The fall in body mass index with increasing age in children withcystic fibrosis parallels the decline in concentrations of IGF-I andits principal binding protein, IGFB3 • The close relation between body mass index and IGF-I concentrationsin cystic fibrosis may reflect poor nutrition or insulin hyposecretion • Nevertheless, low IGF-I concentrations may contribute directly tothe fall in body mass index with increasing age