Deconjugated BAs and secondary BAs can interact with nuclear receptors, including the farnesoid X receptor (FXR), G protein-coupled bile acid receptor 1 (TGR5), vitamin D receptor (VDR), and retinoic acid-related orphan receptor-γt (RORγt), which have been shown to have protective functions in CD by inhibiting intestinal inflammation and preserving epithelial barrier integrity [18,19,20]. Here, VDR is linked to Cowden disease.