How Does Trenbolone Work?

The following article was written by ChestRockwell of Team StackingPlates


As we all know, Trenbolone is almost mythical in its abilities as an anabolic. We have just a wealth of empirical evidence on the boards from many top level bodybuilders with ample experience on the compound. Even so, you still see a lot of contradictory recommendations and experiences.

My goal in this article is to break down the available scientific literature on this compound so that folks have a single resource. As with anything, you are always going to want to combine scientific literature with real-word, “in the trenches”, experiences when forming your conclusions on whether Trenbolone is right for you.

Unfortunately, as we are all aware, Trenbolone studies on humans don’t exist so we must make do with what we have. With that said, I do think that some conclusions can be made and myths laid to rest.

Trenbolone – Part One – Does it Aromatize?

Neumann F (1976)

Trenbolone exerts a variety of anti-estrogenic effects, perhaps through hypothalamic feedback inhibition of the production of testosterone (a substrate necessary for endogenous 17β-E2/Estradiol biosynthesis). The compound is not estrogenic and seemingly not or only weakly progestationally active…additionally, the removal of the methyl group at position 19 of the steroid backbone broadly reduces the susceptibility of 19-nor androgens to aromatisation.

The mechanism(s) through which Trenbolone alters estrogenic activity remain to be elucidated but may be related to the inhibition of endogenous androgen synthesis (presumably through pituitary or hypothalamic feedback inhibition) and/or altered expression or activity of the aromatase enzyme. To summarize, Trenbolone is not a substrate for the aromatase enzyme, but may exert both anti and pro-estrogenic effects, with the bulk being anti-estrogenic.

Trenbolone – Part Two – How Good is it for Building Mass?

The ability for Trenbolone to promote growth is very well known. There are many studies that exist which have shown total body and skeletal muscle mass growth in various animals (bovine, rodents, etc). Here are some of the more famous studies for those wanting to review before we move along.

  • K.Y. Chung, B.J. Johnson – Application of cellular mechanisms to growth and development of food producing animals -J Anim Sci, 86 (2008), pp. E226 E235
  • R.J. Heitzman – The effectiveness of anabolic agents in increasing rate of growth in farm animals, report on experiments in cattle – Environ Qual Saf Suppl (1976), pp. 89-98
  • P.J. Buttery, B.G. Vernon, J.T. Pearson – Anabolic agents some thoughts on their mode of action – Proc Nutr Soc, 37 (1978), pp. 311?315

Now, we can break most of the studies out into two distinct categories – first, those studies which administered Trenbolone alone and those which administered Trenbolone alongside 17β-E2 (Estradiol). Here is where it gets interesting, there is a lot of support for the theory that growth is superior when Trenbolone is administered with Estradiol than when it is administered without. This suggests that Estradiol enhances the anabolic effects of Trenbolone. Although the exact means by which estrogenic substances increase lean mass growth is not entirely understood, most believe it involves an indirect action on the pituitary that causes a release of bovine GH and a direct action on skeletal muscle receptors (Preston, 1987). Whereas androgens seem to exert only a direct growth effect on receptor sites in muscle tissues.

So, a valid argument could be made that the popular “low Test / moderate Mast / high Tren” stack you see preached here often is not ideal for anyone whose primary goal is gaining lean mass.

We’ll talk more about Trenbolone, Estradiol, and fat loss in a later post but please note that most all of these studies show that marbling scores went down when Trenbolone and Estradiol were administered together. This further debunks the “theory” that fat loss is greater when using Trenbolone in a low estrogen state.

Please feel free to review the studies; I’ll post a chart from one of them which reflects the pattern that develops in all of them though (lower marbling when Trenbolone and Estradiol are high).


Trenbolone – Part Three – Trenblone’s Effects on Muscle

So, how exactly does Trenbolone cause muscle growth? Although the mechanisms it uses are not entirely clear, most researchers speculate that Trenbolone exerts direct anabolic effects via AR activation and associated nuclear translocation/transcription (not unlike other androgens). This is depicted in the diagram above and talked about further by Wilson, Lambright et al (2002). And, before we get too far, we must remember that Trenbolone actually has been demonstrated to reduce muscle protein synthesis rates. This is far often misunderstood. The reason growth is demonstrated during use is because it reduces muscle protein degradation rates to a greater extent. Food for thought by those who preach its virtues as the anchor for bulking stacks.

Anyway, where things get really cool though is that some literature suggests trenbolone may actually induce anabolic effects associated with either alterations to endogenous growth factors or the responsiveness of receptors in skeletal muscle to these aforementioned growth factors and IGF-1. This makes me speculate how much of a synergy may exist by using trenbolone alongside exogenous growth hormone?

Where I feel trenbolone shines is during a diet. The reason for this is that it is fantastic, as mentioned before, in preserving lean mass via its effects on the reduction of endogenous glucocorticoid activity. It also may have the ability to suppress amino acid breakdown within the liver. I like to recommend small amounts of trenbolone as part of any extended dieting phase for these reasons.

Trenbolone – Part Four – Trenbolone’s Effects on Adipose Tissue

As a general rule, all androgens will produce secondary effects on lipolysis by binding with androgen receptors located in adipose tissue. Essentially, the stronger the androgen, the higher affinity it will have with binding to these receptors. This bind will stimulate the mobilization of fatty acids, and ultimately the oxidation of them assuming that a caloric deficit is adhered to. Trenbolone by itself, and alongside estrogen, has been shown to reduce subcutaneous fat, intramuscular fat, and decrease muscle marbling (another measurement of intramuscular fat content).

Although, the binding of Trenbolone to androgen receptors in adipose tissue is fairly straight forward, the precise mechanism(s) through which it reduces body fat remain to be determined. Many speculate it may involve a direct stimulation of lipolysis, as demonstrated by an increased expression of enzymes involved in lipolysis in the liver, including enoyl-coA-hydratase (EnoylCoA) and acyl-coA-dehydrogenase.

In various rat studies, there has been an inability for males to gain body weight following trenbolone administration. The speculation here is that this may result from a reduction in total body fat mass or perhaps intramuscular fat content, similar to what has been observed in other species.

  • K. Blouin, A. Veilleux, V. Luu-The, A. Tchernof – Androgen metabolism in adipose tissue: recent advances Mol Cell Endocrinol, 301 (2009), pp. 97?103
  • R.C. Herschler, A.W. Olmsted, A.J. Edwards, R.L. Hale, T. Montgomery, R.L. Preston, et al. – Production responses to various doses and ratios of estradiol benzoate and trenbolone acetate implants in steers and heifers J Anim Sci, 73 (1995), pp. 2873?2881
  • B.A. Reiling, D.D. Johnson – Effects of implant regimens (trenbolone acetate-estradiol administered alone or in combination with zeranol) and vitamin D3 on fresh beef color and quality J Anim Sci, 81 (2003), pp. 135?142
  • J.A. Samber, J.D. Tatum, M.I. Wray, W.T. Nichols, J.B. Morgan, G.C. Smith – Implant program effects on performance and carcass quality of steer calves finished for 212 days J Anim Sci, 74 (1996), pp. 1470?1476
  • M. Reiter, V.M. Walf, A. Christians, M.W. Pfaffl, H.H. Meyer -Modification of mRNA expression after treatment with anabolic agents and the usefulness for gene expression-biomarkers Anal Chim Acta, 586 (2007), pp. 73?81

Some other neat things that have been seen during rodent studies is Trenbolone’s somewhat unique abilities to decrease retroperitoneal (behind abdominal cavity), perirenal (kidney), and other fat depots. I have been trying to get my hands on these studies however they are unpublished, as far as I know.

Time and time again, the lipolytic effects of Trenbolone (Enanthate) have been superior to Testosterone (Enanthate) in comparable exogenous doses. Although I would urge folks not to think of Trenbolone as a “fat burner”, it can definitely assist one’s goals when combined with a proper diet and lifestyle.

Trenbolone – Part Five – Summary and Recommendations

As with most things in life, there is not a single answer to the question “how to best use Trenbolone”. What follows are going to be my recommendations based upon personal experience combined with the literature available on the compound. Although I provide specific dosing strategies, please understand that these are examples for someone with ample experience with AAS. I hold no responsibility for what an individual does with these numbers and they are only used as examples.


Trenbolone is a very potent size growing compound. The mechanisms of growth have been explained thoroughly so I won’t repeat myself here.

I’ve used Trenbolone in various capacities during bulking phases and have found that my body responds best when Trenbolone is not the primary growth “anchor” compound in my stack. As I said earlier, I’m fully aware that others like to run high amounts of Trenbolone during bulks however this has not been the optimal way for me to obtain size, nor many others I’ve coached or been in contact with.

Where Trenbolone shines, traditionally, is when it is an accessory compound and used on concert with a true growth compound such as Testosterone or Nandrolone. The exact ratios vary, however I very much like to aim for a 2:1 ratio so that the Trenbolone can exert its effects without overpowering any other compounds in the stack. Two sample growth stacks are as follows:

  • 150mg/week – Testosterone
  • 400mg/week – Trenbolone
  • 800mg/week – Nandrolone


  • 400mg/week – Trenbolone
  • 400mg/week – Masteron
  • 800mg/week – Testosterone


I feel this is really where Trenbolone shines due to its affinity for reducing endogenous glucocorticoid activity. This means that you can be somewhat aggressive with intake deficits with little concern for proteolysis (specifically from skeletal muscle stores). In most stack configurations, I like to use AAS simply to preserve lean mass so my doses are going to be lower than is generally recommended. If you are using a less severe deficit to recomp then doses can remain higher. I’ll list a couple examples of each below.

  • 150mg/week – Testosterone
  • 300mg/week – Masteron
  • 350mg/week – Trenbolone


  • 400mg/week – Testosterone
  • 400mg/week – Masteron
  • 750mg/week – Trenbolone

As with any sample stacks, there are a lot of considerations to be made. If you are using a compound, such as Trenbolone, for the first time you are going to want to start low and gradually work your way up. Furthermore, it may be in your best interest to start with the short acting (acetate) ester so you can quickly remove if from the system if adverse effects become evident.

It should be noted that the Internet is legendary with potential sides of Trenbolone and I would urge most folks to take these with a grain of salt. Far too often I feel we can become self fulfilling prophecies (i.e. you read about something, believe it will happen, and then it does). In my experience, Trenbolone (although strong) is very low risk as far as producing unwanted effects.

ADDENDUM – via Big Cat

Finally got around to reading Chest’s fantastic write-ups and the links that go with them, and just wanted to point a few things to add:

  • The release of autocrine and paracrine growth factors is likely not a direct effect of Tren, but secondary to its effect on AR, an effect shared by all androgens, but obviously quite potent in the strong AR activator Trenbolone. The combination with GH is therefor no different than for other androgens (well apart from that lovely Tren + GH look the ladies can’t resist ) in that GH’s primary purposes in breaking our plateau of possible physiques is directly related to its ability to increase AR density and thus allow the use of more gear, as well as its effect on boosting those same autocrine and paracrine growth factors, mostly IGF’s and their splice variants (IGF1A, MGF and IGFII).
  • The effect of combining with Estradiol needs to be somewhat nuanced in the sense that these studies are all in female cows or castrated steers. The responsiveness to estrogen will be greater there. It is therefor safe to state that some estrogen will boost results in both muscle gain and especially fat loss (we know estrogen to promote fat loss via both central and local mechanisms, which is why you should keep estrogen moderate until you get below 8%), but not that one necessarily needs a HIGH dose of Testosterone.
  • Trenbolone does bind to the PR with moderate to low affinity, as evidenced by the studies of Ojasoo and Raynaud, but seems to behave more like an anti-progestin. It’s not likely to have much of an effect either way unless in high doses, but could be important for people who suffer from high prolactin for whatever reason (tren itself does not raise prolactin) in that a sudden drop in progestational and estrogenic activity can lead to prolactin becoming active (which is what happens in mothers post-partum) and cause the dreaded lactation. So while gyno from trenbolone, I can tell you this from extremely vast experiences and other experts thoroughly agree with me on this, is non-existent (if you have it the cause lies elsewhere), but it is literally the only hormone when switching from a high to low estro cycle with high tren, that can in fact cause lactation, albeit of a passing nature unless prolactin is kept high, for instance if you have a prolactinoma.

Buying Trenbolone

I use – they stock Trenbolone from some of the top UK/EU labs. Shipping to the UK usually takes 1-2 days and they do ship internationally too. Just send them an email explaining that you got their email address from this website and ask for a price list and they will send over a full list of products and prices.

6 Responses

  1. Dave

    I’ve heard that running low dose Tbol prevents shutdown so you can run it in short (4 week cycle s) without pct or relying on other substances for growth anchor. (.125 mg or lb). Have you ever heard anything similar?


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