19-Nor Prohormones

Prohormone technology has progressed in leaps and bounds since the introduction of androstenedione in 1997. No longer are consumers asking if these items work; now, they ask about brands, dosages, what they should be stacked with, etc. With so many questions being asked by serious bodybuilders, the absence of definitive answers has, unfortunately but not unexpectedly, left the door open to some nutritional nonsense and weird science of the less ethical kind.


The 19-nor steroids are a group of compounds that are precursors to nandrolone. The chemical structure of the 19-nors differs from the more familiar and naturally prevalent androstenes and testosterone by the absence of the number 19 carbon atom and its attached hydrogen atoms. The removal of this chemical group results in a much flatter three-dimensional structure. That structural change in turn results in much more favorable binding affinities for skeletal muscle rather than for prostate and other sexual tissues. In brief, this is important because a high binding affinity means that a substance is more likely to enter the cell and bring about the desired effects.

AST 19-Nor-250

Nandrolone (also known as 19-nortestosterone), the substance into which the 19-nors are to some extent converted by the liver, has a binding affinity that is not only high for skeletal muscle, but that is roughly equal for skeletal muscle and sexual tissues such as the prostate. In comparison, testosterone has a binding affinity as much as 50 times greater for sexual tissues (thus its greater “androgenicity”) than for muscle. So, nandrolone has anabolie effects (which take place in muscle), but less androgenie effects (which occur in sexual tissues).

By now, you may have seen outrageous claims in some advertisements for 19-nor products. While there are still many facts not yet known about the 19-nors, we can tell you straight away that they do not compare in potency to the infamous illegal steroid known as Deca-Durabolin (nandrolone decanoate). The 19-nors may well be partly metabolized to 19-nortestosterone (nandrolone), the steroid base for Deca, but they’re a far cry from their esterified big brother.

Nandrolone itself, although a very effective steroid, is considered to be orally inert, meaning that you’d derive no benefit from taking the drug orally. The 19-nors, however, are orally active, essentially offering an alternative delivery method that is effective judging by the gains in strength and muscle I’ve observed both in people who train at my gym here in England and in the strength athletes I coach.


What advantage is there to taking the 19-nors; is there an advantage to their conversion to nandrolone in the liver; or, is there an advantage to stacking the 19-nors with testosterone-enhancing androstenes? There is a general consensus among athletes and experts that combining androgenic and anabolic hormones results in a greater net gain. Aside from that, nandrolone may offer specific advantages to athletes concerned about estrogen and dihydrotestosterone (DHT), the feminizing and androgenic metabolites of testosterone, respectively, that can have unfortunate side effects (e.g., gynecomastia, hair loss, acne).

The accompanying table lists the differences between testosterone and nandrolone that concern some athletes.

Binding affinity to the muscle androgen receptor High High
Susceptibility to 5-alpha reduction (DHT) High substrate activity, easily reduced Lower activity, not as easily reduced
Resultant biopotency after reduction Less anabolic, more androgenic No change in anabolic activity
The binding affinity of reduced metabolites Increased three to five times Decreased
Susceptibility to aromatization High, approximately 40% Less than 100%
Estrogen formed Estradiol Estrone (weaker)

Nandrolone offers clear advantages over testosterone, as shown in the table. The precursor itself, 19-nor androstenedione, also has a very low aromatization rate (conversion to estrogen) when compared with androstenedione, which is another plus.

Unfortunately, there is currently no relevant published research on the uses or effects of these substances taken orally in any population of humans. Most research pertaining to the 19-nors concerns in vitro and animal studies, in particular horses and pigs, and much of this research tells us that the equine aromatase system is different from humans (no surprise there). Some trials have, however, looked at human tissues, in particular, placental, prostate, ovarian follicular fluid, and fetal adrenal tissues, and these studies may give us some insight into the properties and kinetic pathways of 19-nors.

Estradiol, nandrolone, estrone and 19-nor androstenedione are believed to share a common cellular origin, confirming that they are intermediates produced along the pathway from androgen to estrogen. Evidence that they are metabolites of androstenedione confirms that they have a physiological role in the development of some tissues. It has also been indicated that 19-nor and estrogen synthesis are controlled by cytochrome P-450-dependent enzymes and that, at least in cultured breast carcinoma cells, 19-nor androstenedione inhibits androstenedione aromatization in a dose-dependent manner. This impact on aromatization is a significant attribute of the 19-nors. Their potential as stand-alone anti-aromatase looks promising.

Another worthwhile consideration is the potential influence of luteinizing hormone (LH, which originates in the pituitary gland and acts as a “switch” for sex hormones) on the conversion of the 19-nors to nandrolone. Synthesis of the 19-nors and nandrolone is influenced by LH. This underscores the importance of not overdoing andro products since too much would harm LH production. Products that have a documented effect on LH, such as Tribulus Terrestris, may prove useful in conjunction with the 19-nors.

Athletes should always be fully aware of the possibility that they may fail drug tests after they take 19-nor products, because nandrolone may be detected. There are no acceptable levels of illegal nandrolone. I have already encountered several cases of this. The latest casualty was a powerlifter who tested positive at the recent International Powerlifting Federation World Championships. I personally know this athlete and while, unlike some, he doesn’t claim to be a saint, he did test clean three months before the contest and would have had to have been a complete moron to have even sniffed Deca before the competition! By banning the use of 19-nor products, the International Olympic Committee and other organizations would help to eliminate such scenarios.


Are there any particular advantages to using 19-nordione rather than 19-nordiol? Most likely not. The diols and diones can be interconverted on the “mass balance” principle, meaning that an excess of one would be converted to the other to maintain homeostasis. Combining them may lead to a more effective enzymatic conversion, but we really don’t know. Certainly some of the highest qualified steroid biochemists in the world don’t know the answer to that one, so I’m afraid it’s nothing more than a theory. Of more significance perhaps are the questions of the mode of delivery and ways of extending the half-life. Oral efficacy and degradation have always been big issues with these products, ultimately leading to waste or misuse. We will keep you updated on any significant discoveries that clarify these issues.

So there you have it: a potentially effective ergogen and a promising antiaromatase all wrapped up into one. I believe the 19-nors, particularly when stacked with androstenediol, may be effective. At dosages of 200 milligrams [mg]/day, I have witnessed positive results, without any of the negative side effects that I’ve heard about on an increasingly regular basis from people using excess dosages of andro products. If you up the doses from there for short periods, please use common sense. More is not necessarily better.

If you feel that these substances are worth a try, cycle them, no more than six weeks on, and then four weeks off. Since these compounds are particularly acid sensitive, I would suggest taking them with a sugary drink. Avoid fats and proteins that would likely slow down entry into the bloodstream and lead to an increase in stomach acid with subsequent degradation of the product.

Researcher Michael Mooney has documented the increases in free testosterone with andro products when they’re taken with a sugary, insulin-raising, quick-release drink like grape juice. As he cleverly pointed out, insulin can decrease sex-hormone-binding globulin (SHBG) significantly, which, with andro products, would result in higher free testosterone. Obviously, there are similar implications here. It is probably best to take a single undivided daily dosage in the morning. Circadian rhythms and the positive influence of the 19-nors on aromatization should be considered (endogenous androgens are at their highest early in the day). Although many companies claim that their products cause huge increases in lean tissue, it may be worth reducing sodium intake while on them. Norandrostenedione has been shown to amplify the effects of aldosterone, which potentially could result in fluid retention problems.

In recent months, some problems have come to light regarding the abuse of prohormones. Those problems invariably have been associated with extreme doses (e.g., 1,000 mg per day), mainly of the andro products. It’s too bad, since such foolishness could ultimately lead to the demise of this ground-breaking but sensitive area of sports nutrition. So, if you’re considering trying these products, use your head and start with very low doses.

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