Estrogen Blockers and TRT: Guide and Instructions

Testosterone Replacement Therapy is a perfectly healthy and safe practice, but as we all know, it can raise Estrogen. Is there a need for an AI while on TRT?

Generally, it is believed that the only sex hormone found in men is testosterone (androgen) and in female are estrogen.

Though it may sound unbelievable, both men and women have testosterone and estrogen. Men generally have higher levels of testosterone, while women tend to have higher levels of estrogen..

Testosterone replacement therapy (TRT) is perhaps the most important relationship in this case. TRT is designed to maintain our bodies’ natural testosterone level, while also keeping estrogen levels at an adequate amount.

When the testosterone-estrogen balance has been altered, meaning when there are high estrogen levels, some studies have shown it to impact sexual health.

In men with low levels of testosterone (otherwise known as hypogonadism), their bodies are unable to produce enough testosterone.

As a result, they may experience a number of symptoms such as fatigue, low libido, erectile dysfunction, etc. TRT can help to alleviate these symptoms by increasing the levels of testosterone in their bodies.

In some cases, however, TRT may not be enough to achieve the desired balance of testosterone and estrogen. This is where aromatase inhibitors (AIs) come in. Let’s explore how AIs can help in this situation.

Key Takeaways

  • Aromatase inhibitors (AI) help control excess estrogen production
  • Controlling estrogen levels while on TRT is so important, to avoid aromatase converting the newly injected testosterone into estrogen.
  • It’s important to maintain estrogen levels low but not completely gone. Estrogen is still necessary to have for testosterone production and function.
  • Most common AI currently: Amiridex
  • Other ways to reduce Aromatase activity while on TRT include: diet and exercise

Estrogen Blockers: What are it?

The two key hormones – testosterone and estrogen – have different effects in our bodies. Testosterone is responsible for developing male characteristics such as deepened voice, muscle mass, hair growth, sex drive (libido), etc.

On the other hand, estrogen is responsible for developing female characteristics such as breasts, widened hips, and so on.

Even though we have different levels of these hormones, both men and women need the right balance of testosterone and estrogen in our bodies.

Estrogen is actually an important hormone in men. When the levels of these hormones are not balanced, it can lead to various problems

If you’re on testosterone replacement therapy (TRT), there is a small chance you’re also taking an aromatase inhibitor (AI), an estrogen blocker. AIs are drugs that block the enzyme aromatase, which is responsible for converting androgens (like testosterone) to estrogen and also plays a role in the breakdown of testosterone.

But, why would someone on testosterone replacement therapy need an AI?

As we age, testosterone levels decline naturally. This gradual decrease in testosterone can sometimes lead to a more significant drop, which can cause a number of symptoms such as fatigue, low libido, and erectile dysfunction. TRT is designed to help men maintain their testosterone levels, and in some cases, it can also help to increase them.

However, even with TRT, the levels of testosterone in our bodies can still fluctuate. When testosterone levels are high, there is a likelihood some of it will be converted into estrogen. This conversion happens due to the action of the enzyme aromatase. This is where aromatase inhibitors come in to help.

AIs act to reduce elevated estrogen levels that occurs as a result of testosterone replacement therapy.

Estrogen Levels in Men on Testosterone Replacement Therapy

Although it is commonly referred to as the female hormone, estrogen is present and must be regulated in men as well. But, what exactly is estrogen?


With the evolving popularity of testosterone therapy, estrogen has received popularity in the last decade. It is recognized that men who are on testosterone replacement therapy with experience a rise in their estrogen levels.

Estrogen flows through the body in three forms: E1, E2, and E3. The most potent and well-known form is 17-beta estradiol or E2, which just so happens to be the most important form of estrogen to manage in men undergoing TRT.

If we do not lower estradiol levels, it may block production of other essential hormones that are necessary for testosterone production and potentially impact fertility. [7]

Impact of Too Much Estrogen Production in Men

Aromatase is produced in our adipose (fat) tissue, brain, and testicles and is what converts testosterone into estrogen in our body.

When there is a rise in estrogen (E2) levels, it can actually impact libido (decrease) and cause breast enlargement (gynecomastia). In cases like this, an aromatase inhibitor is necessary to prevent over-conversion of testosterone into estrogen.

Aromatase Inhibitors and Estrogen

Now that we’ve answered the question, let’s discuss the aromatase enzyme.

Aromatase is present in various tissues throughout the body, most notably in adipose tissue, liver, and muscles. This enzyme is responsible for the conversion of androgens (testosterone) into estrogens.

Aromatase inhibitors work by stopping the action of this enzyme. In other words, they block the conversion of testosterone into estrogen.

Estrogen controls the release of gonado-tropin-releasing hormone (GnRH) from the hypothalamus.

When estrogen levels are high, it can feedback and stop the release of GnRH, which then reduces the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH and FSH are both responsible for the production of testosterone in the testicles.

So, by reducing the amount of estrogen hormones in our bodies, we can increase the production of LH and FSH, which will then lead to an increase in natural testosterone production.

This is why controlling your estrogen levels while on TRT is so important, to avoid aromatase converting the newly injected testosterone into estrogen.

NOTE: remember that testosterone therapy is just replacement therapy. It is introducing exogenous testosterone (testosterone that is produced outside of the body) into our system to replace the testosterone that our bodies are no longer producing.

Estrogen Blockers and Testosterone Replacement Therapy

There are three main aromatase inhibitors: Anastrozole (Amiridex), Letrozole (Femara), and Exemestane (Aromasin). Amiridex is perhaps the newest and most common medication used when managing estrogen levels for men on TRT

Armiridex inhibits aromatase enzyme, preventing it from converting testosterone to estrogen. It does not completely eliminate all aromatase, however, so that it does not completely remove all estrogen from the body. Estrogen is required for normal sexual development and functioning, as previously said. Estrogen has been linked to sperm count, testosterone production, and sexual function in men, so it is important to have in the male body. [4]

Ways to Reduce Aromatase Naturally


If you are looking for ways to reduce your aromatase levels without medication, there are a few things that you can do. Look for botanical dietary supplements, which are products made from plants, plant parts, or plant extracts.

Some foods that are rich in aromatase inhibiting properties and have been studied in literature include: cauliflower, kale, black tea, grapefruit (juice), cucumber, coffee, lion’s mane, shiitake mushroom, and spinach. [5]

However, it should be noted that these are not as effective as an AI medication would be and are not a replacement for one. They may still be useful to help control estrogen levels nevertheless.


It’s also important to maintain a healthy lifestyle and diet. Aromatase is produced in adipose (fat) tissue. So, by reducing overall body fat, you can help to reduce the amount of aromatase in your body.

Other Ways to Reduce Aromatase Activity

Injectable testosterone was associated with higher aromatase activity in males, according to one research.

Their study found that levels of estrogen peaked at around the first 3 months, leveled out, and spiked again at around the 9-months, and 18-24 months. [6] So, if you’re concerned about your aromatase levels spiking while on injectable testosterone, you may want to get your levels checked more frequently in the first year or ask your doctor about other testosterone treatment options such as gels or pellets.

Estrogen Blockers: The Final Verdict

It has been shown that some men on testosterone replacement therapy will see a slight rise in their estrogen levels. However, research is still ongoing as to whether this rise in estrogen has any significant impact on the individual long-term. While some doctors may like to start some men on an AI while on TRT and others may prefer to observe estradiol level while on treatment to decide whether an aromatase inhibitor is necessary.

According to the American Urologic Association, they recommend men with low testosterone and gynecomastia be checked for estrogen prior to starting TRT. If they are found to have high estrogen, they may want to consider an AI. If they are not, TRT may be started without an AI and be asked to follow a structured diet or exercise routine to combat a potential rise in estrogen.

It is important to remember that each individual is different. If you have concerns about elevated estrogen levels prior to starting TRT, discuss with your hormone specialist doctor to find the best course to take for your treatment.

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Ramasamy R, Scovell JM, Kovac JR, Lipshultz LI. Elevated serum estradiol is associated with higher libido in men on testosterone supplementation therapy. Eur Urol. 2014 Jun;65(6):1224-5. doi: 10.1016/j.eururo.2014.01.012. Epub 2014 Jan 23. PMID: 24480244.

Taxel P, Kennedy D, Fall P, Willard A, Shoukri K, Clive J, Raisz LG. The effect of short-term treatment with micronized estradiol on bone turnover and gonadotrophins in older men. Endocr Res. 2000 Aug;26(3):381-98. doi: 10.3109/07435800009066175. PMID: 11019903.

Rochira V, Faustini-Fustini M, Balestrieri A, Carani C. Estrogen replacement therapy in a man with congenital aromatase deficiency: effects of different doses of transdermal estradiol on bone mineral density and hormonal parameters. J Clin Endocrinol Metab. 2000 May;85(5):1841-5. doi: 10.1210/jcem.85.5.6583. PMID: 10843162.

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Pastuszak AW, Gomez LP, Scovell JM, Khera M, Lamb DJ, Lipshultz LI. Comparison of the Effects of Testosterone Gels, Injections, and Pellets on Serum Hormones, Erythrocytosis, Lipids, and Prostate-Specific Antigen. Sex Med. 2015 Sep;3(3):165-73. doi: 10.1002/sm2.76. Epub 2015 Aug 12. PMID: 26468380; PMCID: PMC4599554.

de Ronde W, de Jong FH. Aromatase inhibitors in men: effects and therapeutic options. Reprod Biol Endocrinol. 2011 Jun 21;9:93. doi: 10.1186/1477-7827-9-93. PMID: 21693046; PMCID: PMC3143915.


Jimmy Diaz M.S.

Jimmy Diaz M.S. | Writer

Jimmy is a Clinical Scientist from Los Angeles with a background in Chemistry and Reproductive Clinical Science. He is an adrenaline junkie who loves water, winter and wind sports. He is dedicated to advancing the field of reproductive science and providing the best patient care while also exploring new experiences and challenging himself.

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