The effect of cigarette smoking use and cessation on serum insulin-like growth factors

The patterns of risk association between circulating levels of insulin-like growth factor (IGF)-I, and its main binding protein, IGFBP-3, differ between smoking and nonsmoking-related cancers. To investigate this observation further, we measured serum IGF-I, IGF-II and IGF-binding protein-3 concentrations in 232 men and 210 women (aged 55–64 years), and related peptide levels to smoking characteristics. Current smoking was associated with significant reductions in mean IGFBP-3 levels in men assessed by the number of cigarettes smoked daily (P(trend)=0.007) and pack-years smoked (P(trend)=0.03). Mean IGF-I levels decreased with increasing cigarette use in men (P(trend)=0.11). There were no patterns of association between smoking and IGF peptides in women. For male former vs never smokers, there were no differences in mean IGF-I and IGFBP-3 concentrations, suggesting that smoking cessation is associated with normalisation of peptide concentrations.