Whoever said 4-OHT isn't suppressive?
Effects of 4-hydroxyandrost-4-ene-3,17-dione and its metabolites on 5 alpha-reductase activity and the androgen receptor.
Davies JH, Shearer RJ, Rowlands MG, Poon GK, Houghton J, Jarman M, Dowsett M.
Department of Urology, St. Georges Hospital, London, England, UK.
The steroidal aromatase inhibitor, 4-hydroxyandrost-4-ene-3,17-dione (4OHA) and its metabolites, 4-hydroxytestosterone (4OHT), 3 beta,17-dihydroxy-5 alpha-androstan-4-one (metabolite A) and 3 alpha, 17-dihydroxy-5 beta-androstan-4-one (metabolite B) were evaluated as inhibitors of the human prostatic 5 alpha-reductase enzyme and for binding to the rat prostatic androgen receptor. 4OHA and 4OHT were weak inhibitors of 5 alpha-reductase with IC50 values of 15-29 microM. Metabolites A and B had no significant inhibitory activity. 4OHA and metabolites A and B bound weakly to the androgen receptor. The binding affinities (RBA) relative to mibolerone (RBA = 100) were 0.085, 0.485 and 0.016, respectively. However, 4OHT (RBA = 75) was a more potent binder than the endogenous androgen 5 alpha-dihydrotestosterone (RBA = 66). ability of these metabolites, in particular 4OHT, to bind to the androgen receptor explain the in vivo androgenic activity of 4OHA.