The relationship between insulin, IGF-I and weight gain in cystic fibrosis

OBJECTIVE In cystic fibrosis, reduced body mass is related to tow levels of IGF-1 and changes in the IGF binding proteins, Our aim was to determine wh ether these abnormalities are linked to pancreatic endocrine dysfunction. PATIENTS AND DESIGN We measured serum levels of insulin, IGF-1, IGFBP-1, IG FBP-3 and IGF bioactivity in 77 fasting subjects (43 male) mean age 9.6 yea rs (range 2.99-17.98 years). Data were analysed with respect of body mass, puberty and stature and compared with control data established in the same laboratory, RESULTS The mean height standard deviation score (SDS (SD)) was -0.54 (0.97 ) and the body mass index SDS -0.24 (1.09). Both body mass index SDS (r = - 0.40, P = 0.0003) and IGF-1 SDS (r = -0.32, P = 0.009) declined with age. I nsulin levels were also tow and correlated with IGF-1 and IGFBP-3 (r = 0.42 , P = 0.0004, and r = 0.45, P = 0.0002, respectively) whereas levels of IGF BP-1 were inversely related to those of IGF-1 and insulin (r = -0.43, P = 0 .0004, r = -0.52, P < 0.0001). IGF bioactivity was reduced and inversely re lated to IGFBP-1 (r = -0.31, P = 0.009). in multiple regression analysis, b ody mass index SDS was negatively related to age (P < 0.0001) and positivel y related to insulin and IGF-1 (P = 0.04, P = 0.03, respectively). Height S DS was correlated with IGF bioactivity (P = 0.003) and negatively with IGFB P-1 (P = 0.01). CONCLUSIONS We conclude that progressive insulin deficiency may result in r educed IGF-1 levels and IGF-bioactivity and may determine weight gain and s tatural growth in cystic fibrosis.