TGFB1 and chronic obstructive pulmonary disease: Quantification of the active form of TGF-β1 did not differ significantly in the three groups (HC: median = 0, range = 0–65.17; HS: median = 0, range = 0–66.28; COPD: median = 0, range = 0–87.66; pg/ml), demonstrating a low presence of these molecules in the entire population.