NET displays 8 times higher progestational activity than progesterone  . It is also a potent progestogen and binds to the PR with approximately 150% of the affinity of progesterone .  In contrast, its parent compounds, testosterone , nandrolone (19-nortestosterone), and ethisterone (17α-ethynyltestosterone), have 2%, 22%, and 44% of the relative binding affinity of progesterone for the PR.  Unlike NET, its major active metabolite 5α-dihydro-NET (5α-DHNET), which is formed by 5α-reductase , has been found to possess both progestogenic and marked antiprogestogenic activity,  although its affinity for the PR is greatly reduced relative to NET at only 25% of that of progesterone.  NET produces similar changes in the endometrium and vagina and is similarly thermogenic in women compared to progesterone, which is in accordance with its progestogenic activity. 
In clinical studies, cyproterone was found to be far less potent and effective as an antiandrogen relative to CPA, likely in significant part due to its lack of concomitant antigonadotropic action.  Cyproterone was studied as a treatment for precocious puberty by Bierich (1970, 1971), but no significant improvement was observed.  In men, 100 mg/day cyproterone proved to be rather ineffective in treating acne , which was hypothesized to be related to its progonadotropic effects in males and counteraction of its antiandrogen activity.   In women however, in whom the drug has no progonadotropic activity, 100–200 mg/day oral cyproterone was effective in reducing sebum production in all patients as early as 2–4 weeks following the start of treatment.  In contrast, topical cyproterone was far less effective and barely outperformed placebo .  In addition, another study showed disappointing results with 100 mg/day cyproterone for reducing sebum production in women with hyperandrogenism .  Similarly, the drug showed disappointing results in the treatment of hirsutism , with a distinct hair reduction occurring in only a limited percentage of cases.  In the same study, the reduction of acne was better, but clearly inferior to that produced by CPA, and only the improvement in seborrhea was regarded as satisfactory.  The addition of an oral contraceptive to cyproterone resulted in a somewhat better improvement in acne and seborrhea relative to cyproterone alone.  According to Jacobs (1979), “[cyproterone] proved to be without clinical value for reasons that cannot be discussed here.”  In any case, cyproterone has been well-tolerated by patients in dosages of up to 300 mg/day. 
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