One major cause of hepatic sinusoidal obstruction syndrome (HSOS) is the consumption of products containing pyrrolizidine alkaloids (PA). As the use of herbal preparations has increased in China, so has the number of reports of HSOS induced by ingesting PA-containing herbs. The aim of the present study was to investigate the mechanisms by which prednisone and the related factors, transforming growth factor (TGF)-β1 and connective tissue growth factor (CTGF), prevent liver fibrosis and the pathogenesis of HSOS.