Profiles - Steroidology.com
Among athletes Proviron is primarily used as an anti-estrogen. It is believed to act as an anti-aromatase in the body, preventing or slowing the conversion of steroids into estrogen. The result is somewhat comparable to Arimidex (though less profound), the drug acting to prevent the buildup of estrogen in the body. This is in direct contrast to Nolvadex, which only blocks the ability of estrogen to bind and activate receptors in certain tissues. The anti-aromatization effect is preferred, as it is a more direct and efficient means of dealing with the problem of estrogenic side effects.
The anti-estrogenic properties of Proviron are not unique to this compound. A number of steroids have in fact demonstrated similar activity. Dihydrotestosterone and Masteron (2methyl-dihydrotestosterone) for example have been successfully used as therapies for gynecomastia and breast cancer due to their strong anti-estrogenic effect. It has been suggested that nandrolone may even lower aromatase activity in peripheral tissues where it is more resistant to estrogen conversion (the most active site of nandrolone aromatization seems to be the liver). The anti-estrogenic effect of all of these compounds is presumably caused by their ability to compete with other substrates for binding to the aromatase enzyme. With the aromatase enzyme bound to the steroid, yet being unable to alter it, and inhibiting effect is achieved as it is temporarily blocked from interacting with other hormones.
