IGF1 and sarcopenia: The molecular mechanisms involved in this new onset acute sarcopenia are the atrogin-1/muscle atrophy F-Box (MaFbx)/muscle ring finger 1 (MuRF1) pathway, the insulin-like growth factor 1–protein kinase b–mammalian target of rapamycin (IGF-1-AKT-mTOR) and, principally, the myostatin pathway.