IGF1 and chronic obstructive pulmonary disease: A reasonable explanation may be that cytokines produced excessively in AECOPD disturb IGF-1 production, as 24 weeks of infliximab (a TNF-α antibody) treatment reduces serum levels of IGF-1 in COPD patients and TNF-α or IL-1 suppresses IGF-1 bioactivity via induction of IGFBP-1 synthesis both in vitro and in vivo [225, 226].