["Recent studies have suggested that the downregulation of pregnane X receptor (PXR) may contribute to the susceptibility and exacerbation of Crohn's disease (CD). Because bile acid malabsorption is one of the features of CD and bile acids are potential activators of PXR, we explored the relationship between bile acid malabsorption and PXR activities in patients with CD.", 'Twenty-one patients with CD (4 ileal-resected and 17 nonresected), 10 with ulcerative colitis (UC), and 26 healthy controls were studied. Serum biomarkers for the activity of CYP3A4, a target gene of PXR, and for cholesterol and bile acid metabolism were quantified by liquid chromatography-tandem mass spectrometry or enzyme-linked immunosorbent assay.', 'The concentrations of 4β-hydroxycholesterol (4β-HC), a known marker for CYP3A4 activity, and those of 25-hydroxycholesterol (25-HC), another metabolite by CYP3A4, were significantly reduced in all patients with CD, especially in those with the history of ileal resection. The concentration of 7α-hydroxy-4-cholesten-3-one (C4), a marker for hepatic bile acid biosynthesis, was significantly elevated, whereas the levels of fibroblast growth factor 19 (FGF19), a marker for intestinal bile acid flux, were reduced in patients with CD compared with patients with UC and controls. A significant negative correlation was observed between 4β-HC or 25-HC and C4 concentrations in all patients with CD.'] Does bile acid malabsorption deactivate pregnane X receptor in patients with Crohn 's disease?