5beta-孕甾烷-3,20-二酮

5β-Dihydroprogesterone (5β-DHP), also known as 5β-pregnan-3,20-dione, is an endogenous neurosteroid and an intermediate in the biosynthesis of pregnanolone and epipregnanolone from progesterone. It is synthesized from progesterone by the enzyme 5β-reductase. 5β-DHP has been found to act as a positive allosteric modulator of the GABAA receptor (albeit with an affinity for this receptor regarded as relatively low (in comparison to 3α-hydroxylated progesterone metabolites such as pregnanolone and allopregnanolone)) and also as a negative allosteric modulator of the GABAA-rho receptor. In accordance with the former action, it is reported to possess anesthetic, anxiolytic, and antinociceptive effects. 5β-DHP has been found to act as an agonist of the pregnane X receptor (PXR) as well (albeit weakly (EC50 >10,000 µM)), and has been found to regulate uterine contractility through activation of this receptor. Unlike 5α-dihydroprogesterone, 5β-DHP does not possess affinity for the progesterone receptor, and hence, is not a progestogen.