Figure 3.

Representation of pregnane X receptor (PXR) mediated vitamin D catabolism. PXR is activated by various antiepileptic medications and other pharmaceutical agents and induces CYP 24, the enzyme which metabolises active vitamin D₃ to inactive form. Abbreviations: PXR: Pregnane X receptor, DPH: phentyoin, CBZ: carbamazepine, PB: phenobarbital, VDR: vitamin D receptor, PTH: parathyroid hormone, CYP 24: 24-hydroxylase.