 3β-Hydroxysteroid dehydrogenase

3β-Hydroxysteroid dehydrogenase/Δ5-4 isomerase (3β-HSD) () is an enzyme that catalyzes the biosynthesis of the steroid progesterone from pregnenolone, 17α-hydroxyprogesterone from 17α-hydroxypregnenolone, and androstenedione from dehydroepiandrosterone (DHEA) in the adrenal gland.It is the only enzyme in the adrenal pathway of corticosteroid synthesis that is not a member of the cytochrome P450 family.