5α-dihydrolevonorgestrel 5α-dihydrolevonorgestrel 5α-dihydrolevonorgestrel (5α-dhlng) is an active metabolite of the progestin levonorgestrel which is formed by 5α-reductase. it has about one-third of the affinity of levonorgestrel for the progesterone receptor. in contrast to levonorgestrel, the compound has both progestogenic and antiprogestogenic activity, and hence has a selective progesterone receptor modulator-like profile of activity. this is analogous to the case of norethisterone and 5α-dihydronorethisterone. in addition to the progesterone receptor, 5α-dhlng interacts with the androgen receptor. it has similar affinity for the androgen receptor relative to levonorgestrel (34.3% of that of metribolone for levonorgestrel and 38.0% of that of metribolone for 5α-dhlng), and has androgenic effects similarly to levonorgestrel and testosterone. 5α-dhlng is further transformed into 3α,5α- and 3β,5α-thlng, which bind weakly to the estrogen receptor (0.4 to 2.4% of the rba of e2) and have weak estrogenic activity. these metabolites are considered to be responsible for the weak estrogenic activity of high doses of levonorgestrel. relative affinities (%) of levonorgestrel and metabolites compoundprarergrmrshbgcbg levonorgestrel150–16234a, 4501–817–75500 5α-dihydrolevonorgestrel5038a0 ? ? ? ? 3α,5α-tetrahydrolevonorgestrel ? ?0.4 ? ? ? ? 3β,5α-tetrahydrolevonorgestrel ? ?2.4 ? ? ? ? notes: values are percentages (%). reference ligands (100%) were promegestone for the pr, metribolone (a = mibolerone) for the ar, e2 for the er, dexa for the gr, aldosterone for the mr, dht for shbg, and cortisol for cbg. sources: see template. 5α-dihydrolevonorgestrelclinical dataother names5α-dihydrolevonorgestrel; 5α-dhlng; 5α-lngidentifiers iupac name (5s,8r,9r,10s,13s,14s,17r)-13-ethyl-17-ethynyl-17-hydroxy-1,2,4,5,6,7,8,9,10,11,12,14,15,16-tetradecahydrocyclopentaphenanthren-3-one cas number78088-19-4pubchem cid9995794chemspider8171375unii7z4s6960i5chemical and physical dataformulac21h30o2molar mass314.469 g·mol−13d model (jsmol)interactive image smiles cc12cc3(1cc2(c#c)o)cc43ccc(=o)c4 inchi inchi=1s/c21h30o2/c1-3-20-11-9-17-16-8-6-15(22)13-14(16)5-7-18(17)19(20)10-12-21(20,23)4-2/h2,14,16-19,23h,3,5-13h2,1h3/t14-,16-,17+,18+,19-,20-,21-/m0/s1key:bmvirdjapbcapq-wqgsdsccsa-n