cyproterone cyproterone cyproterone, also known by its developmental code name sh-80881, is a steroidal antiandrogen which was studied in the 1960s and 1970s but was never introduced for medical use. it is an analogue of cyproterone acetate (cpa), an antiandrogen, progestin, and antigonadotropin which was introduced instead of cyproterone and is widely used as a medication. cyproterone and cpa were among the first antiandrogens to be developed. this article is about a non-medically used antiandrogen. for the pharmaceutical medication, see cyproterone acetate. cyproteroneclinical dataother namessh-80881; sh-881; nsc-758636; 1α,2α-methylene-6-chloro-17α-hydroxy-δ6-progesterone; 1α,2α-methylene-6-chloro-17α-hydroxypregna-4,6-diene-3,20-dioneroutes ofadministrationby mouth, topicaldrug classsteroidal antiandrogenatc codeg03ha01 (who) identifiers iupac name (1s,2s,3s,5r,11r,12s,15r,16s)-15-acetyl-9-chloro-15-hydroxy-2,16-dimethylpentacyclooctadeca-7,9-dien-6-one cas number2098-66-0 ypubchem cid5284537chemspider4447594 yuniie61q31ek2fchemblchembl142130 ycomptox dashboard (epa)dtxsid3022873 echa infocard100.218.313 chemical and physical dataformulac22h27clo3molar mass374.91 g·mol−13d model (jsmol)interactive image smiles cc(=o)1(cc21(cc32c=c(c4=cc(=o)5c534c)cl)c)o inchi inchi=1s/c22h27clo3/c1-11(24)22(26)7-5-14-12-9-18(23)17-10-19(25)13-8-16(13)21(17,3)15(12)4-6-20(14,22)2/h9-10,12-16,26h,4-8h2,1-3h3/t12-,13+,14-,15-,16-,20-,21-,22-/m0/s1 ykey:dushusljjmdgte-zjpmuuansa-n y (verify) it is important to clarify that the term cyproterone is often used as a synonym and shorthand for cyproterone acetate, and when the term occurs, what is almost always being referred to is, confusingly, cpa and not actually cyproterone. cyproterone itself, unlike cpa, was never introduced for medical use and hence is not available as a medication. pharmacology antiandrogenic activity cyproterone is a potent antiandrogen, similarly to cpa. however, it has approximately three-fold lower potency as an antagonist of the androgen receptor (ar) relative to cpa. like cpa, cyproterone is actually a weak partial agonist of the ar, and hence has the potential for both antiandrogenic and androgenic activity in some contexts. unlike cpa (which is a highly potent progestogen), cyproterone is a pure antiandrogen and is virtually devoid of progestogenic activity. as such, it is not an antigonadotropin, and is actually progonadotropic in males, increasing gonadotropin and testosterone levels due to inhibition of ar-mediated negative feedback on the hypothalamic–pituitary–gonadal axis. due to its progonadotropic effects in males, unlike cpa, cyproterone has been found, in male rodents, to increase testicular weight, increase the total number of type a spermatogonia, increase the total number of sertoli cells, hyperstimulate the leydig cells, and to have almost no effect on spermatogenesis. conversely, it has also been reported for male rodents that spermiogenesis is inhibited and that accessory sexual gland weights (e.g., prostate gland, seminal vesicles) and fertility were markedly reduced, although with rapid recovery from the changes upon cessation of treatment. in any case, the medication is said to not be an effective antispermatogenic agent, whereas cpa is effective. also unlike cpa, due to its lack of progestogenic and antigonadotropic activity, cyproterone does not suppress ovulation in women. other activities both cpa and, to a smaller extent, cyproterone possess some weak glucocorticoid activity and suppress adrenal gland and spleen weight in animals, with cpa having about one-fifth the potency of prednisone in mice. unlike cpa, cyproterone seems to show some inhibition of 17β-hydroxysteroid dehydrogenase and 5α-reductase in vitro. in contrast to cpa, cyproterone shows no affinity for opioid receptors. chemistry