Prohormones UK | A Comprehensive Guide

Date Posted... 21st Feb 2020


Industry News



Prohormones are some of the most powerful legal muscle builders on the market. A prohormone is also known as an androgen prohormone or proandrogen of an anabolic-androgenic steroid (AAS).
What are prohormones?

Prohormones are converted in the body via an enzymatic process which is extremely effective but because of this come with extra side effects compared to other muscle builders on the market. Many prohormones will deliver bigger and stronger results than SARMS, as the desired results are more comparable to anabolic steroids. However, it is worth noting that prohormones are not as strong as anabolic steroids due to the fact they must first convert rather than already being the active anabolic compound.

For example the prohormone 4-Androstenediol or androst-4-ene-3β,17β-diol converts into testosterone at about a 15.76% conversion rate. If you consumed 100mg of 4-Androstenediol daily, then that would give roughly 15.76mg of testosterone daily or 110.32mg a week.

To add confusion to the situation as the supplement industry evolved, so did pro hormones.  A new category of product called a ‘designer pro hormone’ aka ‘designer steroid’ came from this, but most of these kinds of products no longer exist which we will get onto later.

Where did prohormones begin?

A US chemist named Patrick Arnold introduced prohormones to the world in 1996 who developed androstenedione. It instantly created a buzz in the sports world due to publicity from major publications as the product was linked with baseball great Mark McGwire. He was aiming for a new home run record. Because of this Androstenedione was then swiftly followed by 4-androstenediol, 19-norandrostenediol and 1-4-androstadienedione. Each with a different set of results due to different target conversion hormones. Patrick Arnold did not stop there and through his company Ergopharm brought out a new pro hormone 1-testosterone aka 1AD.

1AD was the first legal product to have results comparable to anabolic steroids. Because of this it is safe to say that 1AD was the product that changed the market forever, paving the way for all future prohormones. As supplement companies raced to capitalise on this new sector of the market, newer and more powerful pro hormones followed such as Methyl-1-Testosterone (arguably the strongest product ever) or M1T as it was more commonly known. The reason M1T was so powerful was due to it being 17-alpha alkylated or methylated. This means that the prohormone (in this case M1T) was extremely resistant to being broken down by the liver. This led to rapid strength gains and monstrous muscle gains, even for experienced steroid users!

Sadly, with anabolic substances there is almost always a price to pay for such massive rewards. M1T often caused large amounts of side effects such as very high blood pressure, complete testosterone shut down, severe back acne, reduction of good cholesterol and increases in liver enzymes. These side effects were not guaranteed but one or more was common on a 4-week cycle of M1T.

ProHormones in Detail

Prohormones achieve their results the same way AAS does – effect via androgen receptor. However, it is extremely important to remember that they also can cause a direct stimulation of the body’s estrogenic and progestogenic receptors.

If a prohormone is a strong androgen receptor agonist then you are much more likely to gain increased confidence, increased sex drive and other alpha male type traits whilst using it. However, you also increase the risk for hair loss, aggression and acne. It is worth mentioning that both the benefits and side effects from strong androgen agonists have a massive genetic component and because of this is very hard for pro hormone suppliers to give you perfect personal advice.

Just as some pro hormones are more androgenic than others, some pro hormones can cause less or greater effects via estrogen and progesterone receptors. Whilst this to some extent can help play a role in better muscle building, sex drive and joint lubrication, these can also cause side effects that many men would consider to be the worst ones.

If a product can aromatize (convert to estrogen) then estrogenic side effects can occur. The higher aromatization rate then the more likely you are going to get estrogenic side effects. Such as increased water weight, increased susceptibility to fat gain and worst of all gynecomastia aka gyno, aka boob growth aka bitch tits.

It is important to remember that a prohormone can be estrogenic and androgenic. Equally they can have no conversion to estrogen at all and very low androgenic activity as well, because of this research is key when selecting the right prohormone for you.

It is also worth noting that prohormones promote increased red blood cell production which is why users of prohormones usually have awesome pumps and enhanced vascularity whilst using the products.

PCT for Prohormones


PCT stands for Post Cycle Therapy and there is not a single Prohormone that does not require a PCT. When using ProHormones your body realises that it is getting an external source of testosterone or testosterone equivalent and then begins to stop or limit your natural testosterone production. PCT is used immediately after a ProHormone to help increase natural testosterone back to normal levels.  When our bodies increase testosterone, it tends to increase estrogen at a faster rate too, which can lead to side effects and reduced gains. Because of this, a major part of a PCT is to block the conversion to estrogen helping avoid side effects. Due to these factors, the quality of your PCT will play a major role in how many of your gains stick around. Make sure you know what you’re looking for!

Which is the best Prohormone?

Unfortunately, that is a question that is very personal and is very difficult for any company to answer. People need to consider their goals, the risk reward profile of the prohormone, their genetics – are they likely to suffer from androgenic side effects? And cost of the whole cycle including PCT.

However, jumping straight into the strongest or most hardcore prohormone is 100% what you DO NOT want to do. It is always best to start with something milder but that can still deliver great results.

Eating & Training

Obviously, the aim is to always eat clean and that does not change on Prohormones. You should not use the power of these products as an excuse to be relaxed in other areas of your routine. During a cycle increased water intake is recommended, you may find you get very thirsty during cycles. If the prohormone is methylated, then a protectant such as N-acetyl Cystine (NAC) is a great choice. Protein and food in general can also be increased as your body will be able to better utilise the nutrients. Plus, you will be training that much harder meaning your body will demand the extra nutrients anyway.

During the cycle of prohormones, training volume can be increased but during PCT it is best to reduce the volume and increase the weight to help preserve your muscle and strength gains made on the cycle. This will also help keep cortisol levels low during the PCT. Some say double your training volume when on cycle and half your usual on PCT, but in the end it will come down to personal experience and knowing whats best for you.

The Pro Hormone Ban v1 (2004)

Due to some of the side effects products like M1T could cause, they quickly gained the attention of authorities and regulators. Many industry experts, (apparently at the time including Patrick Arnold) were concerned that strongest products such as M1T would cause more harm than good and eventually would cause them to be forcefully removed from shelves. In 2004 US Congress passed the law “Anabolic Steroid Control Act of 2004” which classed all pro hormones on the US market at the time illegal, classing them the same as illegal anabolic steroids. By early 2005 all of the listed products had been removed from the market.

Pro Hormones 2005-2014

Many of you reading may be thinking but I took pro hormones after 2005. Hell, they are still available today in the US & the UK! Luckily the prohormones on the market today and following 2005 do not carry the same level of side effects that pro hormones like M1T once did.

After 2005 many companies went one of two ways with pro hormones;

  1. Two step conversion prohormones – These prohormones convert twice to get to the target prohormone. For example, the pro hormone 1-Andro was introduced which converts to the 1-androstendione (1-AD – banned in 2004) which then converts to 1-Testosterone (anabolic steroid).
  2. Methylated ProHormones – These ProHormones like M1T use a methyl group at the start of their compound to protect the active portion (that converts to the target hormone) from being broken down and giving a higher conversion rate. The downside of this, like M1T, the process is damaging to the liver.

During this time prohormones or designer prohormones such as Super-Drol came to market which was highly anabolic with very low androgenicity. It could not cause estrogenic side effects and delivered, rapid strength gains, big muscle gains and even some fat loss. Another wildly popular prohormone was Trendione or estra-4,9,11-triene-3, 17 dione, which converted to the extremely powerful anabolic androgen steroid: Trenbolone.

Of course, over time between 2005 and 2014, prohormones and designer prohormones became more advanced. By 2013 many prohormones on the market (particularly in the US) were as strong as some of the compounds banned in 2004.

Pro Hormone Ban v2 – Designer Anabolic Steroid Control Act of 2014 


In 2014, the 113th US Congress passed The Designer Anabolic Steroid Act of 2014 which expanded the list of anabolic steroids regulated by the Drug Enforcement Administration (DEA) to include around two dozen prohormones, designer prohormones and other anabolic substances. It also established new crimes relating to false labelling of steroids. This can bring in up to a $500,000 fine for anyone found to be falsely labelling their anabolic steroid products or for anyone importing, exporting, manufacturing, distributing or found in possession with intent to manufacture or distribute falsely labeled products. Further to this anyone at a retail level can also receive a fine of $1000 per violation. In this legislation a retail level is for products sold or held for sale for each individual unit. Meaning a store with 100 units could be fined $100,000 just for having them in their stock room.

The full list of compounds on this banned list are;

(l) 5a-Androstan-3,6,17-trione;
(li) 6-bromo-androstan-3,17-dione;
(lii) 6-bromo-androsta-1,4-diene-3,17-dione;
(liii) 4-chloro-17a-methyl-androsta-1,4-diene-3,17b-diol;
(liv) 4-chloro-17a-methyl-androst-4-ene-3b,17b-diol;
(lv) 4-chloro-17a-methyl-17b-hydroxy-androst-4-en-3-one;
(lvi) 4-chloro-17a-methyl-17b-hydroxy-androst-4-ene-3,11-dione;
(lvii) 4-chloro-17a-methyl-androsta-1,4-diene-3,17b-diol;
(lviii) 2a,17a-dimethyl-17b-hydroxy-5a-androstan-3-one;
(lix) 2a,17a-dimethyl-17b-hydroxy-5b-androstan-3-one;
(lx) 2a,3a-epithio-17a-methyl-5a-androstan-17b-ol;
(lxi) [3,2-c]-furazan-5a-androstan-17b-ol;
(lxii) 3b-hydroxy-estra-4,9,11-trien-17-one;
(lxiii) 17a-methyl-androst-2-ene-3,17b-diol;
(lxiv) 17a-methyl-androsta-1,4-diene-3,17b-diol;
(lxv) Estra-4,9,11-triene-3,17-dione;
(lxvi) 18a-Homo-3-hydroxy-estra-2,5(10)-dien-17-one;
(lxvii) 6a-Methyl-androst-4-ene-3,17-dione;
(lxviii) 17a-Methyl-androstan-3-hydroxyimine-17b-ol;
(lxix) 17a-Methyl-5a-androstan-17b-ol;
(lxx) 17b-Hydroxy-androstano[2,3-d]isoxazole;
(lxxi) 17b-Hydroxy-androstano[3,2-c]isoxazole;
(lxxii) 4-Hydroxy-androst-4-ene-3,17-dione[3,2-c]pyrazole-5a-androstan-17b-ol;
(lxxiii) [3,2-c]pyrazole-androst-4-en-17b-ol;
(lxxiv) [3,2-c]pyrazole-5a-androstan-17b-ol

Following this the law also states that they can add more compounds at any time. Obviously, they will have to go through a process to do this, but it is highly unlikely if or when they do that other Senators will block compounds from being added to the list.

Post 2014 Pro Hormones

During this time since the ban, prohormones are yet to make a resurgence. The industry has shifted to SARMS in recent years, due to claims of similar or slightly less results with a decreased amount of side effects.
Whether their comeback will be achievable or whether it will even happen will be discussed in our follow up article coming soon – The Future of ProHormones.