20α-dihydroprogesterone 20α-dihydroprogesterone 20α-dihydroprogesterone (20α-dhp), also known as 20α-hydroxyprogesterone (20α-ohp), is a naturally occurring, endogenous progestogen. it is a metabolite of progesterone, formed by the 20α-hydroxysteroid dehydrogenases (20α-hsds) akr1c1, akr1c2, and akr1c3 and the 17β-hydroxysteroid dehydrogenase (17β-hsd) hsd17b1. 20α-dhp can be transformed back into progesterone by 20α-hsds and by the 17β-hsd hsd17b2. hsd17b2 is expressed in the human endometrium and cervix among other tissues. in animal studies, 20α-dhp has been found to be selectively taken up into and retained in target tissues such as the uterus, brain, and skeletal muscle. 20α-dihydroprogesterone names iupac name 20α-hydroxypregn-4-en-3-one systematic iupac name (1s,3as,3bs,9ar,9bs,11as)-1--9a,11a-dimethyl-1,2,3,3a,3b,4,5,8,9,9a,9b,10,11,11a-tetradecahydro-7h-cyclopentaphenanthren-7-one other names 20α-dhp; 20α-hydroxyprogesterone; 20α-ohp; pregn-4-en-20α-ol-3-one identifiers cas number 145-14-2 y 3d model (jsmol) interactive image chemspider 83725 ec number 205-649-5 mesh 20-alpha-dihydroprogesterone pubchem cid 8956 unii 45630a64ac y comptox dashboard (epa) dtxsid10904767 inchi inchi=1s/c21h32o2/c1-13(22)17-6-7-18-16-5-4-14-12-15(23)8-10-20(14,2)19(16)9-11-21(17,18)3/h12-13,16-19,22h,4-11h2,1-3h3/t13-,16-,17+,18-,19-,20-,21+/m0/s1key: rwbruccwzpsbfc-rxrzztmxsa-n smiles c(1cc21(cc32ccc4=cc(=o)cc34c)c)o properties chemical formula c21h32o2 molar mass 316.478 g/mol except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). y verify (what is yn ?) infobox references 20α-dhp has very low affinity for the progesterone receptor and is much less potent as a progestogen in comparison to progesterone, with about one-fifth of the relative progestogenic activity. it has also been found to act as an aromatase inhibitor and to inhibit the production of estrogen in breast tissue in vitro. a single 200-mg oral dose of micronized progesterone has been found to result in peak levels of 20α-dhp of around 1 ng/ml after 2 hours. in another study however, peak levels of 20α-dhp were around 10 ng/ml during therapy with 300 mg/day oral micronized progesterone. 20α-dhp is formed from progesterone in the liver and in target tissues such as the endometrium. it appears to be more slowly eliminated than progesterone. levels of 5α-dhp have been quantified.