Recently, we have shown that the biosynthesis of androste-nol, a potential endogenous ligand for the orphan receptors constitutive androstane receptor and pregnane-X-receptor, requires the presence of enzymes of the steroidogenic path-way, such as 3b-hydroxysteroid dehydrogenase, 5a-reduc-tase and 3a-hydroxysteroid dehydrogenase.