Aerosolized TH delivery prevented pulmonary fibrosis according to either micro-computed tomography scans or histological evaluations, without significant changes in serum THs in a murine model of RILF by attenuating TGF-β1 and phosphorylated Smad2/3 expressions and reducing the accumulation of M2-like macrophages. Here, SMAD2 is linked to pulmonary fibrosis.