Mastoro 100 ™ is unaffected by the aromatase and 5alpha-reductase enzymes and therefore there are no issues with estrogen or with potentiation (increase of effect) in tissues such as the skin and prostate. In fact, Mastoro 100 ™ is somewhat anti-estrogenic due to competing with estradiol at the estrogen receptor, while not itself activating the receptor, and perhaps by likewise competing with testosterone for the binding site of the aromatase enzyme, thus reducing conversion. This is a benefit when only a moderate amount of aromatizing steroids are used and no other anti-estrogen is used. It is not, however, sufficient to fully deal with high doses of aromatizing steroids, or at least not with typical doses of Mastez 100; and is unnecessary when more effective anti-estrogens are employed.