World-renowned anabolic authority, William Llewellyn has written and rewritten the definitive book on steroids. His series of ANABOLICS books have become the most trusted steroid and performance drug reference book of its kind. For over 15 years Llewellyn has uncovered and compiled cutting-edge insider's information from actual drug manufacturers, dealers, and users from all over the world, guaranteeing up-to-date information. During his fifteen years of anabolic research, Llewellyn has made several important scientific discoveries. His latest discovery of arachidonic acid has been patented for its anabolic properties and its "use as a method of increasing skeletal muscle mass."

Publication Date: February 20, 2006

Nothing in this article is intended to take the place of advice from a licensed health professional. Consult a physician before taking any medication.

Not too many steroids have an air of mystique about them quite like trenbolone. It is one of those agents that you will hear talked up aggressively by some guy in the gym, to later find he has not even tried it himself yet. The bodybuilding literature is full of strong, unusual, and often-inaccurate statements about this drug, and consequently an air of misunderstanding has begun to cloud our view of trenbolone. The unusual history of this compound, including prolonged periods of very limited availability and high selling prices, has no doubt played a part in shaping the view of this steroid in the minds of athletes. It seems when anything is out of reach, overly expensive or both, people start looking at it in a different way. I therefore thought it would be a good idea to take a closer look at the physical properties of trenbolone, as well as its current state of availability and use.

Structurally trenbolone is a derivative of nandrolone, carrying two additional double carbon bonds at positions 9 and 11 (hence the prefix "tren", short for tri-en). The activity of trenbolone differs from that of its parent hormone considerably however. To begin with, trenbolone cannot aromatize to estrogen. The delta-9 group present on its structure occupies a bond necessary for aromatization of the A-Ring to be possible. Unless this group is removed metabolically, which it does not appear to be, estrogen synthesis is impossible in the body. Although nandrolone is a weak substrate for aromatase, estrogen levels can still rise during use. With trenbolone we actually expect a lowering of serum estrogen levels, as it should suppress endogenous testosterone release (the primary substrate for estradiol in men).

Although derived from nandrolone, trenbolone is comparatively far more androgenic than this steroid. In fact it is several times stronger in this regard than our primary androgen testosterone as well (1). The first contributing factor to this of course is that trenbolone is a strong binder of the androgen receptor. This trait is also characteristic of its parent nandrolone, which is several times more active than testosterone in this regard. Androgen binding is in fact further enhanced by the introduction of double bonds in delta-9,11 (2), which makes trenbolone an even more potent agonist of the androgen receptor than nandrolone. Perhaps more significant though is the fact that unlike nandrolone, the strong receptor binding potency of trenbolone is not diminished in androgen sensitive tissues by 5-alpha reductase. Trenbolone does not seem to undergo 5-alpha reduction in humans to any appreciable degree at all, which is evidenced by the fact that the major urinary metabolites of trenbolone all possess the original tri-en structure with an intact delta-4 group (3). So trenbolone retains its original potency as it enters cells in androgen target tissues with high 5AR concentrations, as this enzyme is not affecting it. These factors work together to allow trenbolone to be a potently androgenic steroid, instead of a primarily anabolic one in nature like nandrolone. .

It has been reported in other bodybuilding literature that trenbolone does not exhibit any activity as a progestin in the body. I am not certain where this belief originated, as trenbolone does appear to exhibit the classic progesterone receptor binding ability that is characteristic of nandrolone and its derivatives. One study looking at the bovine uterine progesterone receptor for example found trenbolone to be a very potent binder, startlingly even more so than progesterone itself (4). Another looking at the binding of various compounds to the androgen, estrogen, progestin, mineral corticoid and glucocorticoid receptors found trenbolone to be a more potent binder of the progestin receptor than nandrolone (5), a steroid normally noted for its usual activity in this regard. What does this mean for trenbolone? I don’t think it really means that much. Trenbolone clearly doesn’t cause gyno, water retention or fat buildup, which one might attribute to estrogenic or progestational activity. So whatever slight action it does have as a progestin on paper doesn’t amount to all that much in the real world. The absence of estrogen may be a significant factor, as progesterone is believed to cause gyno by enhancing estrogen’s stimulation of mammary gland growth (6). Perhaps when trenbolone is taken with other aromatizable compounds it could affect a person’s sensitivity level to gyno and water/fat retention. This seems logical, at least in a technical sense, although admittedly I have seen no evidence to support this.

Trenbolone (17beta-hydroxyestra-4,9,11-trien-3-one)

The potently androgenic and non-aromatizing nature of trenbolone makes it an extremely effective hardening and cutting agent. In fact, it is thought of as unmatched in its capacity as a body-sculpting steroid. Many competitive bodybuilders similarly find it indispensable to any good pre-contest cutting stack. For this type of purpose I doubt another steroid would serve you better. Many people do additionally find they make very good muscle gains with trenbolone. It is a potent muscle-builder, although we should probably not consider it an ideal mass-builder when used alone. The absence of estrogen is an important factor, as this trait seems integral in this type of steroid. This probably has to do not only with water retention but also interactions between estrogen and muscle glucose utilization, GH release and androgen receptor proliferation. Today we are finally starting to understand why this hormone is needed for optimal growth. Trenbolone is probably still the most potent muscle-building agent of all the non-estrogenic steroids though, and admittedly is quite unusual in its potency in this regard. But I would still think that if mass were the goal and you were choosing only one steroid, testosterone, Dianabol or Anadrol would be more productive every time in terms of overall size, weight and muscle mass gain.

As mentioned in the opening of this article, trenbolone has been plagued by periods of manufacturing inconsistency, high prices and scarce availability since it first hit the market in the early 80’s. There is probably little need to revisit in detail the rise and fall of Finajet in the 1980’s, or the demise of Parabolan in 1997. Clearly the colorful history of trenbolone is well discussed. But today’s situation is no less interesting, as we are in a unique situation. For the first time in four years we have a legitimate injectable trenbolone again, as the Mexican veterinary drug firm Laboratories Ttokkyo has recently started producing Trenbol, a 10 ml bottle of trenbolone acetate (TA) in the strength of 75mg/ml. This product is not cheap, and usually sells for upwards of $150 a bottle. Reportedly Denkall is working on a similar item, and there are some reliable underground generics floating about as well that sell for a better price and usually supply a comparable amount of TA. There have been some questions about raw material supply lately though, and whether or not both types of product would remain on the market. This discussion was heightened by the recent removal of Trenbol from Ttokkyo’s website (www.ttokkyo.com.mx), which is making a lot of people nervous that this product may be on the way out. Hopefully this is just a website problem and not a repeat of the fate that fell on Finajet and Parabolan. If these products do dry up, trenbolone will still be available, but in the form of cattle implant pellets. In Part II of this article I will take a closer look at these unusual products, as well as the various methods utilized by bodybuilders in an effort to effectively use them.

1) Pharmacological and endocrinological studies on anabolic steroids. Neumann F. Environ Qual Saf Suppl 1976 (5) 253-64

2) Unique steroid congeners for receptor studies. Ojasoo, Raynaud. Cancer Research 38 (1978) 4186-98

3) Disposition of 17 beta-trenbolone in humans. Spranger, Metzler. J Chromatogr 564 (1991) 485-92

4) Characterisation of the affinity of different anabolics and synthetic hormones to the human androgen receptor, human sex hormone binding globulin and to the bovine progestin receptor. Bauer, Meyer et al. Acta Pathol Microbiol Imunol Scand Suppl 108 (2000) 838-46

5) Unique steroid congeners for receptor studies. Ojasoo, Raynaud. Cancer Research 38 (1978) 4186-98

6) Progesterone is not essential to the differentiative potential of mammary epithelium in the male mouse. Freeman, Topper. Endocrinology. 1978 Jul;103(1):186-92