uk bodybuilding coach

Posted 6 months ago

Modulating oestrogen levels

Over the past three years or so, there has been a big shift in the industry in how assisted bodybuilders control oestrogen levels. In the past, assisted bodybuilders might have used medications such as aromatising inhibitors (e.g., Arimidex) or selective oestrogen receptor modulators, known as SERMs (e.g., Tamoxifen) to stop their oestrogen levels getting too high.

However, in today’s industry, oestrogen levels can be controlled through the addition of Masteron or Primobolan (DHT derivatives) to an individual’s stack. Although this is widely accepted and done, many will not know exactly how the addition of these steroids helps modulate our oestrogen levels, nor the potential risks that result from letting oestrogen run too low. Therefore, the purpose of this article is to give an insight as to how these steroids, as well as Arimidex and Tamoxifen, modulate our oestrogen levels and their use within a bodybuilders stack design. Please note that the following article is written in a hypothetical sense and should not be deemed or taken as advice in any way.

Testosterone conversion to oestrogen

Oestrogen is the primary sex hormone in females, although that does not mean it is not needed in males. Oestrogen will regulate metabolic rate, fuel metabolism, and insulin sensitivity. It plays an important role in bone maturation, supports healthy HDL/LDL levels, maintains energy levels, and much more.

In case you didn’t know, testosterone can be converted to oestrogen by an enzyme called ‘aromatase’, and the more testosterone there is in your body, the more that can subsequently be converted to oestrogen. How much and at what rate you might ask? Unfortunately, that will be completely person dependant upon your testosterone levels, how much oestrogen you can tolerate and your bodies individual genetic response.

Whilst oestrogen is necessary for males as well as females, in males the problem stems when oestrogen levels increase past a certain point to which unwanted side effects start to be seen, such as the formation of breast tissue (gynecomastia) and body fat accumulation. Luckily, research done in recent years has highlighted that those side effects aren’t dictated by the total level of oestrogen in the body but are instead determined by the ratio of androgens to oestrogen found in the body. That is, the side effects are dependent on the level of testosterone relative to oestrogen in the body. Personally, I know that if I see a 1:4 or 1:5 ratio of testosterone to oestrogen, I do not see any oestrogenic side effects. This is something I’ve been able to assess by getting my bloods checked, for example: seeing testosterone at 50nmol/m and oestrogen at 200-250pmol/l. Therefore, if one were able to manipulate their usage to stay within a similar ratio, the side effects may not be seen. This is however different from person to person, so please don’t take this advice as gospel as I’ve seen some clients be able to handle a 1:6 or 1:7 without any issues. This should reiterate the inter-individuality and that there is no “one size fits all” approach.

AI’s, SERMs and lowering oestrogen

In the past, oestrogen has been seen as the ‘enemy’, so assisted bodybuilders tried to bring their levels down using Arimidex or Tamoxifen, which have their clinical use in treating women with breast cancer. Both will decrease the levels of circulating oestrogen but will do so in different ways: on the one hand, Arimidex works by blocking the aromatase enzyme itself and thus reducing total levels of circulating oestrogen; on the other hand, Tamoxifen works by binding to oestrogen receptors, inhibiting oestrogen’s subsequent ability to do so.

Although these will both decrease the level of circulating oestrogen effectively, their usage does come with a slight cost to health, as they will have direct impact on your HDL (good cholesterol) and LDL (bad cholesterol). That is, you will have decreased levels of HDL and increased levels of LDLs. Of course, if left unchecked, these can increase one’s risk of arthrosclerosis. Therefore, in today’s industry, we see these medications used much less to help modulate levels of oestrogen, and instead there has been an increase in the use of Primobolan/Masteron to do so.

Primo/Mast and lowering oestrogen

This process can be slightly complicated to explain, so let me break it down into simple, understandable, and digestible chunks. Using the analogy of key and lock mechanisms, let’s suppose testosterone is the key, and the aromatase enzyme is the lock. When testosterone docks with the aromatase enzyme the aromatisation process can begin: the key is inserted into the lock, it turns the lock and ‘opens’ the door. Still with me?Now, when we think of Primobolan and Masteron, imagine that they are both also like a key, with a similar molecular structure to testosterone, but with some subtle differences. In layman’s terms, we can still insert this key into the lock, but we cannot turn the lock and open the door. Instead, nothing happens. This subsequently means that because Primobolan or Masteron are occupying the binding site (lock), they act as a competitive inhibitor, so that testosterone cannot “get in and open the door”. On the whole, what this means is that there is less testosterone docking with aromatase and thus less total oestrogen being produced in the body.

One could then know that they don’t need to use an AI or a SERM to modulate their oestrogen levels and can instead simply use DHT derivatives to almost do the same thing. I think this is where the confusion has emerged, because people just simply haven’t understood how oestrogen can be modulated through each process and have thus assumed that it was through the same mechanism.

Stack design

In summary, using Primobolan or Masteron seems to have a similar affect at lowering oestrogen without some of the health side effects observed, which favours their use. It is at this point that you may then wonder which would be better to use between these two DHT derivatives. It’s at this point that you may wonder which would be better to use, Masteron or Primobolan. It’s probably one of the most common questions that gets asked around, but it can depend on so many factors. If one were to be in a contest prep, they may favour leaning more towards Masteron for its cosmetic effects. Anyone who is experienced with steroid use will tell you that Masteron will give a drier look to the physique, if/when someone is truly peeled. The only problem with Masteron is that I often see it faked by underground labs. For example, some of them might cut corners and blend it with other things such as testosterone, which as you have already guessed, will increase oestrogen levels as opposed to helping manage them.

With this in mind, there is an ongoing argument in the industry about how Primobolan is superior to all steroids in its binding to the androgen receptor. For the most part, it is widely accepted that this is the case. Therefore, if someone wanted the best of both worlds – lowering oestrogen and having more capacity to grow – it could be argued that Primobolan would be the right choice to make all year round.

In a contest prep scenario, taking both would give you the benefits you’re looking for: a drier look and an increased ability for growth. However, a lot of people do complain about the cost of Primobolan, which is why they would choose to favour using Masteron. If the Masteron you are getting is real (confirm through blood work), then based on their molecular structure and what they will both do with aromatase, one could just as easily choose Masteron over Primobolan and get the same desired effect from an oestrogen management perspective.

As for using AI’s or SERMs, I feel that they are not necessarily needed in one’s stack and would only tend to use them ad hoc I were to see gynecomastia symptoms for a short period, whilst I adjusted the rest of the stack design.


We have spoken of some of the benefits that may come from favouring DHT derivatives over AIs or SERMs, but this choice doesn’t come without its own implications and drawbacks.
Firstly, if one is using high levels of Masteron, Primo or both, this can drastically reduce your oestrogen levels to the point where they are too low. This would be damaging, given the importance of oestrogen in managing metabolism, fuel, insulin sensitivity, and other essential bodily processes (as referred to at the start of this article). The only way you’d be able to accurately know whether your oestrogen levels were too low would be through getting your bloods checked.

Secondly, I’ve also observed that HDL (good cholesterol) levels can get quite low when using high levels of Masteron, Primo or both, although it doesn’t seem to elevate LDLs (bad cholesterol) quite so much. Of course, having low levels of HDLs for a prolonged period this isn’t healthy, but then again, no one ever said taking steroids was healthy. In this case, given the negative impact on HDLs seen by using Ais, SERMs and DHT derivatives to control oestrogen, you could look at it from a “which is the lesser of two evils?” perspective. You could then argue that having more androgens in your system will give you a greater total capacity for growth, making DHT derivatives more favourable in this case.

In summary, over the years the way assisted bodybuilders have controlled their levels of oestrogen has changed. From the use of breast cancer medications to the use of DHT derivatives, we are now at a point with research at which we can understand how/why oestrogen levels can be modulated, and how much oestrogen we can handle. Which route to go down then becomes a decision that falls on the individual, a decision which they should make based on their needs, wants, and individual responses.

Vaughan Wilson Bsc Hons