Serum levels of eleven growth factors, including brain-derived neurotrophic factor (BDNF), leukemia inhibitory factor (LIF), fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor (VEGF), nerve growth factor (NGF), epidermal growth factor (EGF), and stem cell factor (SCF), were measured in COPD patients at baseline. This evidence concerns the gene BDNF and chronic obstructive pulmonary disease.