3A-hydroxysteroid dehydrogenase (HSD3B) is a bifunctional enzyme from 3-beta-HSD family that catalyzes the oxidative conversion of delta(5)-ene-3-beta-hydroxy steroid as well as ketosteroids, and is essential for the biosynthesis of all classes of hormonal steroids. HSD3B catalyzes the transformation of pregnenolone to progesterone, 17-alpha-hydroxypregnenolone to 17-alpha-hydroxyprogesterone, DHEA to 4-androstenedione, dihydrotestosterone to 5-alpha-androstane-3 beta,17 beta-diol, dehydroepiandrosterone to androstenedione and 5-alpha-androstan-3 beta,17 beta-diol to 5-alpha-dihydrotestosteron. HSD3B is highly expressed in placenta, skin, mammary tissues etc and localize to ER/mitochondrion membranes as single-pass membrane protein wherein it plays critical role in lipid metabolism as well as steroid biosynthesis pathways. Among its different isoforms, HSD3B1 is abundantly expressed in human placenta and is implicated progesterone biosynthesis for the maintenance of pregnancy. HSD3B1 polymorphism has been linked to prostate cancer susceptibility, an increased risk of benign prostate hyperplasia, and essential hypertension.