What are SERMs and AIs?

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Both SERMs (Selective Estrogen Receptor Modulators) and AIs (Aromatase Inhibitors) were originally designed to treat individuals suffering from a range of Estrogen related issues including breast cancer, ovarian problems, and postmenopausal osteoporosis. Depending on the specific drug, you can expect a distinct effect on the production and/or binding affinity of Estrogen in the body, and even in certain places such as the breasts.

SERM and AI usage in men serves a different purpose and is quite popular, predominantly when those men are using Performance Enhancing Drugs (PEDs). SERMs and AIs can manage Estrogenic side effects brought on by steroids while on cycle, and also help “turn on” the testicles and resume endogenous Testosterone production to normal levels post cycle (Post Cycle Therapy).


What you should know about Estrogen?

We know from clinical studies (and anecdotal evidence), that Estrogen is extremely beneficial to both men and women. For Performance Enhancement, Estrogen needs to be optimal to facilitate growth. Estrogen does not directly stimulate muscle protein synthesis, but it has been found to enhance the Anabolic Response following exercise. The mechanism in which it acts is that Estrogen can promote inflammation, and Hypertrophy is primarily an inflammatory response initially.

We also know that Estrogen is neuroprotective. Meaning, it can help protect the brain and the neural functions of the body. This attribute can help protect the body against illnesses such as Alzheimers. Interestingly, Estrogen is also linked to intelligence. Additionally, Estrogen is also great for cardiovascular health. It is a great protective measure against atherosclerosis, which is the buildup of fats, cholesterol, and other substances in your arterial walls. Lastly, Estrogen also plays a massive role in the male libido. 

So, logically we would want as much Estrogen as possible, correct? Healthy, and better sex? Not really. We know from countless anecdotal PED cases that having too high of Estrogen levels can be exceptionally detrimental for men. With it, bringing adverse effects such as Gynecomastia (Bitch Tits), increased emotional instability, sexual dysfunction, and blood pressure issues. 


When are SERMs and AIs Needed? 

SERMs and AIs are invaluable for anyone using PEDs, as they will massively impact performance, aesthetics, and general health. Both can help with the management of Estrogen, however, they function differently by mechanism of action. An Aromatase Inhibitor (AI) will inhibit the Aromatase Enzyme, which are located in fat cells, from converting Testosterone into Estrogen. This is why we’ll often see Steroid and SARM users supplement with an AI to block their Estrogen levels from rising too high. Having sky-high Estrogen levels is great for Anabolism, however, can quickly lead to adverse side effects such as Gynecomastia. 

A Selective Estrogen Receptor Modulator (SERM) has a different mechanism of action than an AI. SERMs bind to Estrogen Receptors throughout the body, which will inhibit free-flowing Estrogen in the blood from binding to the receptors and acting upon them. SERMs will also increase both FSH (Follicle-stimulating hormone) and LH (Luteinizing hormone) which in turn will induce and increase the production of endogenous Testosterone. 


The different SERMs and AIs 

There are a few commonly used SERMs and AIs, and they will almost always come in oral/pill form. Depending on your individual needs, you could use them on cycle and/or after you have finished a cycle. Exposing your body to a compound like Testosterone that Aromatizes, will usually always require some form of Estrogen management at some point. 

On cycle, you’re going to use an AI, which will lower Estrogen significantly more than a SERM can. Most Steroids and some SARMs will raise Estrogen levels and can cause Gyno and other side effects if unmanaged. If you’re genetically Estrogen sensitive, you may need a higher and even daily dose, however a conservative dose, a few times per week should generally be sufficient. There is no one size fits all dosage protocol, as everyone responds differently to medication/drugs. If you’re looking to get on a bodybuilding stage, you might need to suppress Estrogen and Progesterone quite significantly (or completely) to achieve that “dry”, award winning esthetic. 

As mentioned before, a SERM will typically be used after the cycle (post cycle), as part of a Post Cycle Therapy (PCT) protocol. SERMs are also particularly good at lowering Estrogenic effects in breast tissue, while not affecting Estrogen activity in other parts of the body. This means that compared to AIs, they aren’t as harsh on your lipid profile. They will also stimulate the production of FSH and LH in the male body, which will increase the function of the Leydig Cells in the testicles, initiating and increasing Testosterone production, as well as Intratesticular Testosterone, which is essential for male fertility.


Popular SERMs 

SERMs are essential for SARM and Steroid users as part of a proper Post Cycle Therapy, and especially popular amongst SARM users because SARMs tend to not suppress Testosterone and/or raise Estrogen as much as Anabolic-Androgenic Steroids can.


Nolvadex (NOLVAGEN)

Nolvadex (Tamoxifen Citrate) has been an invaluable drug  in the bodybuilding scene by men and women for decades now. Used predominantly as part of a PCT protocol, it can also find its way into an on cycle protocol as well. Nolvadex is regularly used to severely crash Estrogen before a bodybuilding competition. It can also be used as a “bridging” drug after using an Aromatase Inhibitor, since the use of an AI will cause a rebound effect, which can be mitigated by Nolvadex. 

As a SERM, Nolvadex will not lower the circulating levels of Estrogen in the body, but rather prevent Estrogen from binding to, and acting on, the Estrogen Receptors located in breast tissue. Nolvadex will however still allow for Estrogen to bind to Estrogen Receptors in other parts of the body such as the liver – which is beneficial for general health (particularly relating to  Cholesterol). 

Another quality of Nolvadex is its ability to increase Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH). This will cause an increase in natural Testosterone production. It does this by binding to the Estrogen Receptors in the Hypothalamus, which signals for more Testosterone to be produced so it can be converted into Estrogen. This makes Nolvadex essential to include in a proper PCT protocol. 


Possible Dosage: 

  • On Cycle: Men @ 10-20 mg/day, only use as needed to mitigate side effects for the duration of the cycle.
  • Post Cycle Therapy (PCT): Men @ 40 mg/day for 2 weeks, 20mg/day for another 2-4 weeks, run concurrently with Clomid. HCG may be run for 10 days before Clomid and Nolvadex, depending on the required PCT. Start PCT accordingly after all anabolic compounds have been fully cleared from the body.
  • Post Cycle Therapy (PCT): Women @ 40 mg/day for 4 weeks, run concurrently with DHEA @ 25-50 mg/day for 4-12 weeks.


When looking at Clomid (Clomiphene Citrate), on paper it seems to be a better drug than Nolvadex. Both lower Estrogenic activity, increase Testosterone, and possibly decrease water retention. However, Nolvadex will upregulate progesterone receptors, meaning it will not be a good product to use after running a 19-Nor steroid, or Anadrol. Clomid on the other hand, will not do this, and Clomid will also not lower IGF-1 levels like Nolvadex tends to. The only problem with Clomid is what is referred to as the “Clomid-crazies”. As the name suggests, Clomid can negatively affect mental clarity for some users.

Clomid binds to the Estrogen Receptors in the breast tissue (not as strongly as Nolvadex) which can lower the risk of sides like Gyno dramatically. Clomid will still allow for Estrogen to be active in the liver, which of course is great for lipid values. Clomid will also bind to the Estrogen Receptors within the Hypothalamus, causing an increase in Testosterone production via increased LH and FSH levels. 

Possible Dosage: 

  • On Cycle: Men @ 50 mg/day, only as needed to mitigate side effects for the duration of the cycle.
  • Post Cycle Therapy (PCT): Men @ 100 mg/day for 2 weeks, 50 mg/day for another 2 weeks, run concurrently with Nolvadex. HCG may be run for 10 days before Clomid and Nolvadex, depending on the required PCT. Start PCT accordingly after all anabolic compounds have been fully cleared from the body.
  • Female Fertility Aid Protocol: @ 50 mg/day, five days into the menstrual cycle, for five consecutive days. Increase to 100 mg/day on the next menstrual cycle if unsuccessful. Repeat for 5-6 menstrual cycles before looking for alternative options.

Raloxifene Hydrochloride (EVISTA)

Evista (Raloxifene Hydrochloride) could be considered Nolvadex 2.0, as it was developed in 1997 and has a number of improvements over its SERM predecessors (Nolvadex/Clomid). It acts similarly to Nolvadex by lowering Estrogen activity in breast tissue. Evista differs by having other attributes, such as being able to increase bone density. Additionally, it will raise Testosterone levels more so than Nolvadex can. 

Raloxifene has proved to suppress Estrogenic activity more effectively than Nolvadex in breast tissue. This makes Evista the goto SERM for stopping and reversing Gynecomastia. Much like Nolvadex and Clomid, it functions as a Testosterone booster by binding to the Estrogen receptors in the Hypothalamus, which will cause the release of LH and FSH, increasing natural Testosterone production. 

Possible Dosage: 

  • On Cycle Protocol: Men @ 30 mg/day, only use as needed.
  • Gynecomastia Treatment Protocol: Men @ 30 mg/day for 4-6 weeks should be sufficient to reverse gynecomastia symptoms.

Popular AIs

AIs are invaluable to Steroid users, especially for those who use stronger, or larger amounts of, aromatizable compounds. As aforementioned, having too much Estrogen can cause havoc in the body with the adverse related side effects.

Aromasin (AROMAGEN)

Aromasin (Exemestane) is uniquely a “suicide” inhibitor, meaning it will bind to the Aromatase enzyme and “kill” it, rendering it inactive. In response the body will produce more, however, by leaving the existing enzymes inactive, there is zero risk of an Estrogenic rebound. Aromasin can lower Estrogen levels by upto 85%. While not as strong as other AIs, it is still the most commonly used Aromatase Inhibitor due to its unique suicide inhibitor activity, and its general effectiveness for most PED users. 

Compared to the SERMs aforementioned, AIs like Aromasin will act upon all Estrogen within the body in a way that will prevent Estrogen from being created. This means that not only can it cease Gynecomastia, but it can mitigate other Estrogenic side effects such as emotional instability, water retention and the related high blood pressure . 

Possible Dosage: 

  • Men @ 12.5-25 mg/every 2-4 days, only as needed to mitigate side effects for the duration of the cycle.

Arimidex (AROMAGEN)

Arimidex (Anastrozole) was originally developed to treat breast cancer. In the performance enhancing world, bodybuilders have found using Arimidex to be quite useful to manage Estrogen levels when on cycle. It is a stronger Aromatase Inhibitor than Aromasin, however it acts a bit differently. Aromasin is a suicide inhibitor, whereas Arimidex will just inhibit the Aromatase enzyme from converting Testosterone into Estrogen.

By binding to the Aromatase Enzyme, Arimidex prevents Estrogen from being created at the source, which allows for greater control of Estrogen. Importantly, some Estrogen is still essential for general health, and especially for anabolism. There is a balance of Estrogen that is ideal for everyone (not too high, not too low) and that will differ person to person. Arimidex is a better option than Letrozole (Unless you need to completely crash Estrogen). 

Possible Dosage: 

  • Men @ 0.5-1 mg/every other day, only as needed to mitigate side effects for the duration of the cycle.

Letrozole (LETROGEN) 

Letrozole (Femara) is the strongest Aromatase Inhibitor available and will completely crash Estrogen. It is rarely used due to its potency, generally used as a last resort for those who are genetically prone to being highly sensitive to Estrogenic side effects, and/or for some bodybuilders at the end of a cutting cycle that are preparing for competition. Letrozole acts similarly to Arimidex by its mechanism of action, but is significantly stronger than other AIs.

Possible Dosage: 

  • Men @ 0.5-1 mg/every other day (EOD), only as needed to mitigate side effects. 
  • This drug is meant for short term use only! Generally 7-14 days to stop and reverse Gyno, or during the last few days pre-contest of a bodybuilding competition prep – only if it is needed.

Which AI or SERM should You use? 

For male Steroid and SARM users, SERMs and AIs will be an invaluable part of your stack, both on and off cycle to mitigate the Estrogenic side effects of these compounds. Women will rarely need on-cycle AI or SERM supplementation unless they are in the competitive bodybuilding scene. It is always wise to keep both a SERM and an AI on hand when using Steroids or SARMs as a safety measure, in case they are needed. 

There is no ideal dosage or compound recommended for everyone, as we all have different genetics, and respond differently to drugs, training, nutrition, etc. So, on cycle, start with the lowest possible dose of a mild Aromatase Inhibitor like Aromasin, and increase dosage – if needed. If you notice the onset of Estrogenic side effects, you may need to switch from Aromasin to Arimidex if you are highly sensitive. If daily Arimidex does not mitigate Estrogen, you may need to add a SERM into your protocol. Dosing protocols are different for everyone, and fine tuned by trial and error. 

Estrogen is a very anabolic hormone, as Anabolism (muscular hypertrophy) is an inflammatory process that is enhanced by Estrogen. So, to gain quality lean muscle tissue, you will need an ideal amount of Estrogen. Too much will bring adverse side effects, and too little, or none at all will inhibit anabolism and can be detrimental to general health, sex drive, and well being. 

Another option to help decrease Estrogenic side effects on cycle would be to increase the frequency of injections from once or twice a week to every other day (EOD) or even daily, as daily administration is the closest protocol to mimic natural testosterone production. Daily injections can become arduous, but will keep your blood serum levels stable and will bring less side effects, to the point of not needing a SERM or AI on cycle. Additionally, daily injections will allow you to use a significantly lower amount of compounds and only require a 27 gauge, ½” long, 1 ml insulin syringe to administer your hormones, which is far less invasive than the traditional 23-25 gauge, 1-1.5” long, 3 ml syringe.

Proper Post Cycle Therapy (PCT) is pretty straight forward. For men it will always require at least one SERM, generally Nolvadex, and possibly the addition of Clomid and initial HCG therapy, depending on the cycle. For women, generally Nolvadex and DHEA supplementation will be sufficient for PCT. By following a proper PCT protocol you will help your body return to natural homeostasis as quick as possible with the least amount of adverse physiological and mental side effects. Not following a proper PCT, and/or neglecting the need to supplement with AIs/SERMs on cycle is irresponsible and can lead to a number of adverse side effects and irreversible bodily harm.

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