Upregulated IGF-1 expression and/or signaling is present in (1) patients with idiopathic fibrotic lung diseases, such as idiopathic pulmonary fibrosis (IPF) and late-stage sarcoidosis [81], (2) patients with secondary fibrosis, such as silicosis, pneumoconiosis, drug-induced pulmonary fibrosis, mustard gas-induced pulmonary fibrosis, systemic sclerosis-related interstitial lung disease, and rheumatoid arthritis-related interstitial lung disease [82–89], and (3) animal models of lung fibrosis induced by bleomycin, paraquat or silica challenge, and radiation [90–92]. Here, IGF1 is linked to rheumatoid arthritis.