What is Aromatization of Testosterone, & What To Do About It


Written by Elite HRT on September 12, 2021

Medically reviewed by

Camille Freking, Regulatory Affairs Specialist, MEDICAL ADVISOR

The human body has millions of different chemical reactions that occur on a regular basis. From cellular respiration which gives us energy, to the chemical breakdown of foods we eat, chemical reactions are the basis of all life. While chemical directions are vital to life, other chemical reactions can be potentially harmful to the body’s everyday functions.

Some of the most potent chemicals within the body are hormones. Hormones are chemical compounds that signal cells within the body to regulate different functions. These potent chemical messengers have very specific functions thanks to their complex structures, but when these hormones are altered through chemical reactions it can drastically alter what they do within the body. 

Below is a closer look at the aromatization of testosterone into estradiol and how that plays a role in your health. Hormones are the basis of many functions within the body and making sure that the body has an appropriate hormone balance is vital for your wellbeing. 

What is Testosterone?

Testosterone is a hormone that is commonly known as the “macho” hormone. The main contributing factor to this perception is that testosterone is the main male sex hormone. While testosterone undoubtedly has effects on one’s ability to have a “macho” muscular physique, it is also responsible for many other functions within the body. 

Testosterone also plays a role in increasing the likelihood of competitive and aggressive behaviors, a healthy libido, body hair growth, fat distribution, and much more. Understanding that testosterone impacts more than just muscle mass is important to note because testosterone is a hormone that plays an important component in your overall well-being. 

Testosterone is mainly produced within the testes of men, but it is also produced in lesser amounts through the adrenal glands on top of the kidneys. Women even produce testosterone through the adrenal glands and ovaries in small amounts. 

What is Estrogen?

Estrogen is the main sex hormone in women and it plays an important role in libido, menstrual cycle regulation, bone density, and the development of secondary sex characteristics like breast tissue. Estrogen is an important signaling hormone in women from adolescence through menopause. 

Estrogen is mostly secreted from the ovaries in women but it is also secreted in small amounts through the adrenal glands. In men, estrogen is made in small quantities in the testis and through other chemical means. 

What is Aromatization?

In your chemistry classes, you most likely remember learning about substitution reactions, catabolic reactions, and anabolic reactions. These reactions are quite prevalent in the human body and one chemical reaction, in particular, can significantly impact your hormonal balance. That chemical reaction is known as aromatization. 

Aromatization is a chemical reaction that converts testosterone into estrogen and androstenedione into estrone. Aromatization occurs within the body due to an enzyme known as aromatase that reduces the barriers to the conversion. Essentially, it makes it easier for testosterone to be converted into estrogen. 

Aromatization is a multistep reaction that involves the oxidation of a methyl group. The aromatase enzyme allows these steps to occur more readily and without it, it would take much longer for the reaction to occur. 

In the context of hormone balance, when aromatization occurs, the concentration of testosterone decreases, and the concentration of estrogen increases until an equilibrium is reached. 

For many people, aromatization is occurring at a normal rate and the body is still able to maintain its hormone balance. In some cases, however, aromatization could lead to imbalance and subsequent unwanted characteristics. 

When Can Aromatization Cause Problems?

Aromatization on its own is not an inherently harmful reaction, and in fact, aromatization is thought to be an important method by which men produce healthy levels of estrogen. A problem can occur when testosterone levels are elevated. 

In other words, aromatase readily converts more testosterone into estrogen, which can lead to estrogen accumulation. 

For men, aromatization can cause a condition known as gynecomastia which is the development of breast tissue due to too much estrogen. Certain treatments like testosterone replacement therapy can worsen these rare events by increasing the amount of estrogen available within the body. 

Aromatization can also occur in women. Some forms of cancer can be worsened by estrogen, and when aromatase is left unchecked, there may be an increase in estrogen levels within the body. Many cancers in women are acquired later in life post-menopause. Without ovaries producing estrogen on a consistent basis, aromatization can become a significant contributor to estrogen levels. 

What Can You Do About Aromatization?

While countless reactions occur within the body, there are ways to modify them. One of the easiest ways humans have to modify these reactions is by creating drugs that target specific enzymes that catalyze those reactions. 

In the case of aromatization, there is a class of drugs known as aromatase inhibitors that work by rendering aromatase less effective at doing its job. A great way to think about aromatase inhibitors is to think about the enzymes as little factories that convert testosterone to estradiol. Inhibitors gunk up the factories and shut down the factories. The way this is achieved however can differ. 

What Are the Different Types of Aromatase Inhibitors?

Aromatase inhibitors come in two different types: steroidal and non-steroidal aromatase inhibitors. Understanding the differences between the types of inhibitors available can allow you to be better versed in the available treatments available for the unwanted conversion of testosterone into estrogen. 


Steroidal aromatase inhibitors are immensely potent because they essentially shut down aromatase and inactivate it. This is accomplished because steroidal aromatase inhibitors resemble the testosterone molecule which enables it to readily covalently bind with the enzyme. Once bound, the inhibitor stays within the enzyme and essentially acts as a blockade where testosterone can no longer interact with the enzyme.

Inactivating aromatase permanently can be a necessary step to take if estrogen levels could worsen your health, such as the situation with estrogen-sensitive breast cancer. Because these aromatase inhibitors are irreversible, they tend to be utilized more sparingly. 


Non-steroidal aromatase inhibitors act similarly to steroidal inhibitors; however, they do not bind covalently with the active site of the enzyme. This allows non-steroidal aromatase inhibitors to be reversible and is a major reason as to why these drugs tend to be a first-line treatment. 

Aromatase Inhibitors and TRT

The world of hormone replacement therapy is ever-growing, and throughout the history of testosterone replacement therapy, many things have been learned. One of those is that testosterone therapy can lead to the formation of breasts, or gynecomastia, as a side effect. 

At face value, it may seem ironic that injecting male hormones can cause the formation of man boobs. The reality is that aromatization can be to blame. As you increase blood concentrations of testosterone through TRT, you also increase the amount of estrogen needed to be in circulation for aromatase to reach an equilibrium. 

With this drive to establish equilibrium, aromatase converts more testosterone and can elevate estrogen levels to a point that it signals breast tissue growth in men. 

Aromatase inhibitors may be prescribed to treat or prevent gynecomastia due to TRT, and it has shown to be effective. Some clinics may even prescribe an aromatase inhibitor to try and prevent the formation of gynecomastia and hormone imbalance during testosterone replacement therapy

While aromatase can be detrimental to men, it is important to note that it plays an important role in establishing healthy male estrogen levels. Estrogen in men plays an important role in libido, sexual functioning, and even bone density. 

If utilized unsupervised, an aromatase inhibitor could reduce estrogen levels to a point where you may experience unwanted side effects since the dose inhibits the formation of the estrogen needed to function at your best. 

Because of the delicate balancing act of testosterone and aromatase function, it’s important to put your therapy in qualified hands, such as with a hormone specialist clinic like Elite HRT

With a team ready to walk you through your hormone replacement journey, you can rest easy knowing that you will have just the right balance for you and your specific needs. 

Get started today by filling out our intake form here


In summary, the aromatization of testosterone is a naturally occurring reaction that converts testosterone into estradiol. The reaction occurs in both men and women and plays an important role within the body. Even though aromatase is an important molecule in the body, it isn’t to say it can’t be problematic. 

Excess estrogen in men can lead to the formation of breasts which is at no fault to the person’s lifestyle and can place unwanted stress on self-esteem. 

Aromatase inhibitors help by reducing the effectiveness of aromatase which can be exactly what is needed to re-establish hormone balance. 


Testosterone insufficiency in women: fact or fiction? | BUMC

Estrogen’s Effects on the Female Body | Hopkins Medicine

Aromatase inhibitors: mechanism of action and role in the treatment of breast cancer | PubMed