Nolvadex is a drug commonly referred to as an anti-estrogen. Actually, Nolvadex is an estrogen antagonist, meaning it competes with estrogen at estrogen receptor- sites. This prevents the active estrogen from entering its receptor and creating an estrogenic complex capable of activity. Since many AAS aromatize (covert to estrogen) to some degree, the control of feminizing side effects (males should pay attention here) is important. Males normally have a very low estrogen level. During AAS cycles, due to aromatization, estrogen levels rise considerably. This elevated estrogen level can cause feminizing side effects such as increased fat deposits, water retention, and gynecomastia (growth of breast gland tissue and painful tumors under the nipple). As a rule, it is more the ratio of androgens-to-estrogens than the simple increase in estrogen that actually initiates feminizing side effects.
It is important that the reader realizes that Nolvadex does not decrease estrogen production and that it simply blocks estrogen receptors. For this reason the sudden discontinuance of Nolvadex will allow the increased level of circulating estrogen to merge with the newly freed receptors and do feminine things to the body.