The apparent contradiction between IGF-1 and lung disease in preclinical studies and epidemiology can be partly explained by the fact that preclinical models primarily measure IGF-1 in the lungs, as mentioned in asthma and IPF, while epidemiological studies primarily assess the level of peripheral serum IGF-1, which may have different effects on immune response and airway inflammation. Here, IGF1 is linked to idiopathic pulmonary fibrosis.