However, Costes et al. found that the phosphorylation levels of IGF-1 downstream factors Akt, GSK-3β, and 70-kDa ribosomal protein S6 kinase in the hypoxemic COPD group were lower than those in the normoxemic group after 8 weeks of endurance exercise; furthermore, the muscle CSA was significantly increased in the normoxemic group of COPD patients. Here, IGF1 is linked to chronic obstructive pulmonary disease.