testosterone steroids

Posted 1 year ago

Introduction to AAS- Testosterone

It’s no secret that anabolic androgenic steroids (AAS) are a big part of the bodybuilding community and that their usage is increasing globally each year. I still remember being a young naïve adult, just jumping on the steroid cycle that my friend suggested I tried, without too much knowledge behind what I was taking.

It was only after years of research and completing my undergrad that I began to understand the physiology behind AAS and the effects they can have on the body. Therefore, my aim for this article is to simply introduce testosterone and AAS, how it works in the body and things you should be aware of if/when choosing to use it.

What are they?

AAS are a class of medication that contain a synthetically manufactured form of the hormone testosterone, or a related compound that is derived from this hormone: similar in structure and action. It’s worth noting that all AAS are derived from testosterone. Therefore, in order to understand AAS, it makes sense to start looking at testosterone first, to understand its basic function.

As I am sure you are well aware of, testosterone it is the primary male sex hormone that is manufactured in the testes. The effects of this hormone become most evident during puberty, when increased levels of testosterone cause huge physiological and physical changes in the male body, such as deepening of the voice, growth of bodily and facial hair, and the development of sexual organs. These changes are what we refer to as the “androgenic” properties of the hormone.

In addition to those androgenic changes, increased levels of testosterone will also cause “anabolic” changes within the body which include (but are not limited to) enhanced protein synthesis, which leads to an increase in muscle mass. The average male will produce 2.5-11mg of testosterone per day, which would give a reading between 8.9–28 nmol/l in a blood test. This is strikingly higher levels than females, who will only produce about 0.25mg per, which would give a reading between 0.2–2 nmol/l in a blood test day, which explains the differences in males’ and females’ abilities to gain muscle mass.

How does it work?

The actual mechanisms by which testosterone elicits its effects are fairly complex. The majority is transported around the body in a bound form, specifically to Sex Hormone Binding Globulin (SHBG) or Albumin. It’s important to note, though, that when testosterone is in its bound form, it is somewhat rendered inactive from being able to act upon cells.

However, when it is free in the blood, testosterone will interact with various cells within the body such as skeletal muscle, skin, scalp, kidneys, liver, and prostate tissues. In this form, it can only interact with cells that have a specific receptor, which is commonly known as the Androgen Receptor. Think of this receptor like a lock for which testosterone is the key. The receptor or lock can only be activated by a particular hormone (key), which in this case is testosterone.

This interaction directly alters the genetic make-up of a cell, and in muscle mass, it will increase the formation of two primary contractile proteins: actin and myosin. In Layman’s terms, the lock turns the key which promotes the cell to stimulate muscle growth. Once this process is complete, testosterone is released to go back into circulation and interact with other tissues. If we use another example such as the kidneys, this interaction will work to stimulate an increase in red blood cell production, and we refer to this as an androgenic side effect.

It’s worth noting that adipose tissue (fat cells) is androgen responsive, and as such, testosterone supports the mobilisation of fat as a fuel source. This is up there with one of the main reasons why assisted body builders can get extremely lean whilst they keep all the muscle mass they have.

In addition, testosterone has an indirect mechanism of action that is muscle protective: that is, it binds to the glucocorticoid receptor (GR). Let me explain. Glucocorticoids, such as cortisol, have the exact opposite effect to androgens on muscle cells, as they promote muscle breakdown. Testosterone, however, can bind to the GR and act as a somewhat competitive inhibitor. This means that glucocorticoids can’t bind to the GR and promote muscle breakdown. Therefore, testosterone indirectly protects muscles from being broken down.

Altogether, you can see how having increased levels of testosterone would be deemed as beneficial for males who have the goal of increasing their muscle mass. Not only does it promote muscle growth, but it also hinders muscle breakdown, and facilitates fat tissue mobilisation. However, it’s not just rainbows and daisies.

Oestrogen Aromatisation

How many times have you heard a bodybuilder talk about gynecomastia? Probably more times that you can count. That is because the hormone testosterone can be converted to oestrogen, which if you didn’t know, is the primary sex hormone in females.

Oestrogen is structurally very similar to testosterone but has a slight alteration which is done by the aromatase enzyme. This can be found in various regions of the male body including adipose tissue (more noted here in the nipples), liver, gonads, central nervous system and brain.

In a natural male with normal levels of testosterone, the total amount of oestrogen that is produced is generally not significant to one’s body disposition of body fat and may even be beneficial to things such as cholesterol values. However, if produced in large amounts, it has the potential to cause unwanted side effects such as the formation of breast tissue (gynecomastia) and body fat accumulation.

In case it isn’t clear, these are all side effects that you’d want to avoid as a male testosterone user. Luckily, research done in recent years has highlighted that those side effects are dictated by the ratio of androgens to oestrogen found in the body. Meaning control the level of testosterone vs the level of oestrogen. Personally, I know that if I see a 1:4 or 1:5 ratio of androgens to oestrogen, I do not see any oestrogenic side effects. This is something I’ve been able to assess by checking out my blood work and seeing testosterone at 50nmol/l and oestrogen at 200-250pmol/l. Therefore, if one were able to manipulate their usage to stay within a similar ratio, the side effects should not be seen. This is however different from person to person, so please don’t take this advice as gospel.

These most recent findings have – to an extent – eliminated the need for using oestrogen lowering drugs such as Arimidex or Tamoxifen (Novadex). Steroids which convert to oestrogen are in fact the best for mass building, mainly due to the indirect side effect of increased glucose utilisation, growth hormone secretion and androgen receptor proliferation. Therefore knowing that controlling the androgen to oestrogen levels in the body can help maximise muscle growth, without needing to take additional drugs to mitigate side effects, is a positive thing.

DHT conversion

As I alluded to earlier not all the testosterone in your body is free to do what it likes, as most of it “exists” in its bound form, and some of it is converted to oestrogen. However, it is important to note that the potency of testosterone is considerably increased in androgenic tissues (skin, scalp, prostate etc) when it converts to dihydrotestosterone (DHT).

This is the most potent steroid found naturally in the human body, as it is in fact three to four times stronger than testosterone. DHT can occupy the androgen receptor in a cell and have a greater impact on the genetic make-up of that cell than its parent hormone, testosterone. This would mean we surely don’t want to have high levels of DHT floating around the body if we can help it from a health perspective.

Testosterone is converted to DHT by an enzyme called 5-alpha-reductase (5-AR). In tissues that have high levels of 5-AR, very little testosterone will make its way to the androgen receptor without being converted to DHT. In some regards, this local potentiation of testosterone activity might be unwelcomed by many, such as those who experience undesirable side effects such as acne or male pattern baldness.

Nevertheless, DHT isn’t all that bad. It does play an important role in organisation and functioning of the central nervous system (CNS). There is little doubt that the ability of the body to adapt to training is reliant on the interactions between the neuromuscular system, which includes all the muscles and nerves serving them. The main point here is that if you were to try and reduce levels of DHT in the body you may experience a decrease in performance.

The drug finasteride is often used to lower 5-AR and thus DHT levels in the body as a “cure” to male pattern baldness. However, knowing the important role that DHT plays in the body, this wouldn’t seem like a sensible approach to take. Instead, I would personally just keep test low and use other compounds that were less androgenic, such as Nandrolone.

Of course, with prolonged exposure and usage of AAS, you may encounter some side effects. Having read the information above you should see why it is imperative to try and monitor any potential side effects and mitigate them through supplementation or manipulation of dosage and/or compounds. There are of course many different compounds but we will not be going into that into this article.

In summary, testosterone has a variety of roles within the body. Very little of this hormone is free within the body to act upon androgen receptors which are present in a number of tissues and organs. Some will also be converted to oestrogen which if not controlled can cause a lot of unwanted side effects and then some will also be converted to DHT which is far more potent than its parent hormone.

Vaughan Wilson Bsc Hons


Llewellyn, W. (2017). ANABOLICS 11th Edition (11th ed.). Molecular Nutrition.