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 E2Tooltip estradiol (medication)) and have weak estrogenic activity. These metabolites are considered to be responsible for the weak estrogenic activity of high doses of levonorgestrel.
See also 5α-Dihydronorethisterone 5α-Dihydroethisterone 5α-Dihydronandrolone 5α-Dihydronormethandrone
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