A Look into the Most Commonly Used Anti-Estrogens and Aromatase Inhibitors


by Josh Hodnik

Not much more than a decade ago, body builders relied mostly on pharmaceutical grade steroids from Europe and veterinary grade steroids from Mexico. The cost of most drugs, aromatase inhibitors more specifically, were much too expensive for most people to afford, so drugs such as clomiphene, tamoxifen, and aminoglutethimide were used to control estrogen levels when using anabolic steroids. Within the past decade, countless UGL’s and research chemical companies have popped up. These companies are able to obtain raw materials for aromatase inhibitors at a very cheap price, and this has driven the price down dramatically for these drugs. Now that there is a larger selection of drugs available to keep estrogen levels in check. I will now review the most common ones that are available.

Tamoxifen Citrate

This anti-estrogen has been used for decades to control estrogen related side effects in steroid users. Tamoxifen is a mixed estrogen agonist/ antagonist. It binds to estrogen receptors in certain tissues, which blocks estrogen from binding to these receptors, leaving it inactive. Many bodybuilders have chosen not to use tamoxifen in fear that it can reduce muscle gain. The belief is that tamoxifen will slightly lower IGF-1 levels, which could interfere with gains. The use of anabolic steroids elevate IGF-1 levels, so if there is in fact a slight reduction from tamoxifen use as some people believe, IGF-1 levels would still be higher than normal, and a reduction in gains should not be a concern. Tamoxifen is fairly inexpensive, easy to find, and rarely counterfeited. It is a very effective choice to control estrogen related side effects, such as water retention and fat accumulation when low to moderate doses of anabolic steroids are used. Average dose is 20mg daily.

Clomiphene Citrate

Similar in structure to tamoxifen, clomiphene is also a mixed estrogen agonist/antagonist. It is referred to as a selective estrogen receptor modulator (SERM.) Estrogen receptors require the hormone to be present, but it will also need activation of parts of the receptor known as AF-1 and AF-2. Clomiphene has the ability to block this activation. Clomiphene is known for its ability to stimulate testosterone production. This is achieved by blocking the inhibition of estrogen by the hypothalamus and pituitary. Clomiphene has shown to be effective for long-term treatment of low-testosterone levels. Similar to tamoxifen, clomiphene is effective in combating elevated estrogen levels when taking low to moderate doses of anabolic steroids. The cost of clomiphene is low and it doesn’t have a negative impact on blood lipid profiles, which is often a concern with many aromatase inhibitors. The downside to this drug is that estrogen related side effects, such as water retention and fat accumulation will often occur if high doses of steroids are used. Many male users of clomiphene have reported mood swings and depression. Average dose: 50-100mg daily.


Anastrozole is in a class of drugs known as aromatase inhibitors (AI’s.) AI’s block the conversion of aromatizable steroids to estrogen. This is a completely different mechanism of action that occurs with anti-estrogens such as tamoxifen and clomiphene, which block estrogen receptors in some tissues, and activates estrogen receptors in others. Anastrozole can reduce estrogen levels enough to allow larger amounts of anabolic steroids to be used without the side effects that accompany elevated estrogen levels. It is possible to lower estrogen levels too much if anastrozole is dosed too high, so estrogen levels should be monitored with blood work. Years ago, anastrozole was too expensive for most people to afford. The price in 2001 was over $300 for 28 1mg tablets. Today, anastrozole can be found for an average price of $40 for 30 1 mg tablets. The price drop has allowed many more steroid users to use an AI such as anastrozole. The availability of AI’s today have allowed bodybuilders to dose testosterone and other steroids higher than they could with using anti-estrogen. Anastrozole and other AI’s have contributed to bodybuilders of this era to become bigger, leaner and drier than ever before. Anastrozole is an excellent choice in keeping estrogen levels in check when taking moderate to high levels of anabolic steroids. This drug is much more effective than the previously discussed anti-estrogens, tamoxifen and clomiphene.


Aromatase inhibitors are categorized as either a Type I or Type II AI. Type I inhibitors such as exemestane are considered steroidal compounds, and AI’s such as anastrozole and letrozole are in the Type II group, which are non-steroidal drugs. Exemestane is about 65% efficient at suppressing estrogen, compared to 50% with anastrozole. Exemestane possesses a quality that letrozole and anastrozole do not. At the same dose that is used to lower estrogen, it will raise testosterone levels by about 60%, and also help increase free testosterone by lowering levels of sex hormone binding globulin (SHBG) by about 20%. This makes exemestane a very good choice for post cycle therapy. This diverse AI has a stronger estrogen suppressing ability than anastrozole, and it has the ability to significantly raise testosterone, giving it a place in post-cycle therapy. Average dose: 10mg-12.5mg twice daily.


This aromatase inhibitor surpasses exemestane and anastrozole as being the most potent AI used today by bodybuilders. It has shown an ability to not only prevent gynocomastia, but to reduce current cases of gyno. Letrozole has been known to cause joint dryness and pain. Estrogen is necessary for healthy joints and a healthy immune system. If joint pain and/or over training syndrome occurs while taking letrozole, it is possible that its being dosed too high, and the dose should be backed off until the joint pain subsides. This potent AI is the most effective aromatase inhibitor available, and its ability to reduce gyno that is already present makes this compound a double-edged sword.

The variety of drugs available today to lower estrogen levels, compared to just limited number of anti-estrogens available twenty years ago, have contributed to bodybuilders stepping on stage looking shredded and dry, while carrying more muscle mass than ever before.


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