Cyproterone acetate is a synthetic derivative of 17-hydroxyprogesterone, and acts as an androgen receptor antagonist as well as a weak progesterone receptor agonist with weak progestational and glucocorticoid activity. Some portion is metabolized by hydrolysis to cyproterone and acetic acid. However, unlike many other steroid esters, cyproterone acetate is not extensively hydrolyzed, and much of its pharmacological activity is attributed to its acetate form. Cyproterone acetate has approximately three times the anti-androgenic activity of cyproterone. Cyproterone acetate inhibits the steroidogenic enzyme 21-hydroxylase and to a lesser extent 3β-hydroxysteroid dehydrogenase, both of which are needed to synthesize endogenous corticosteroids such as cortisol and aldosterone, and it may reduce cortisol production, though there is great individual variability in this effect.
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