Ok, I looked it up so we can stop the debate.
Nandrolone Decanoate - also known as Deca Durabolin - Injectable (also avaiable as a transdermal gel)
This drug is unique in that 5 a-reductase, the enzyme which converts testosterone to the more-potent DHT, actually converts Nandrolone Decanoate to a less-potent compound. Therefore this AAS is somewhat deactivated in the skin, scalp, and prostate, and these tissues experience an effectively-lower androgen level than the rest of the body. Therefore, for the same amount of activity as another drug at the androgen receptors (ARs) in muscle tissue, Nandrolone Decanoate gives less activity in the scalp, skin, and prostate. Thus, it is the best choice for those particularly concerned with these aspects.
Its effectiveness at the androgen receptor of muscle tissue is superior to that of testosterone: it binds better. Yet, it gives only about half the muscle-building results per milligram. This is a result of its being less effective or entirely ineffective in non-AR-mediated mechanisms for muscle growth. It also appears less effective or entirely ineffective in activity on nerve cells, certainly on the nerve cells responsible for erectile function. Use of Nandrolone Decanoate as the sole AAS often results in complete inability to perform sexually. These problems can be solved by combining with a drug that does supply the missing activity: e.g. testosterone.
Nandrolone Decanoate (Deca) is proven to be a progestin. This fact is of clear importance in bodybuilding, because while moderate Nandrolone Decanoate -only use actually lowers estrogen levels as a consequence of reducing natural testosterone levels and thus allowing the aromatase enzyme less substrate to work with, Nandrolone Decanoate nonetheless can cause gyno in some individuals. Furthermore, just as progesterone will to a point increase sex drive in women, and then often decrease it as levels get too high, high levels of progestogenic steroids can kill sex drive in male bodybuilders, though there is a great deal of individual variability as to what is too much.
Incidentally, this progestogenic activity also inhibits LH production, and contrary to common belief, even small amounts of Nandrolone Decanoate are quite inhibitory, approximately as much so as the same amount of testosterone.
To some extent, Nandrolone Decanoate aromatizes to estrogen, and it does not appear that this can be entirely blocked by use of aromatase inhibitors. Indeed, aromatase may not be involved at all in this process (there is no evidence in humans that such occurs) with the enzyme CYP 2C11 being the more likely candidate for this activity.
Nandrolone Decanoate is moderately effective at doses of 200 - 400 mg/week. The long half-life of Nandrolone Decanoate makes it unsuited to short alternating cycles, but suitable for more traditional cycles, with a built-in self-tapering effect in the weeks following the last injection.
Pharmakinetics studies with Nandrolone Decanoate - Deca show that it is more desirable to administer it on a weekly basis rather than bi-weekly or monthly if the most consistent blood levels of the steroid are desired. While blood levels of Nandrolone Decanoate - Deca rise in several hours, the mean half-life of the Nandrolone Decanoate is approximately 20 percent longer than testosterone cypionate.
Note that dosing information in the package Nandrolone Decanoate has recently been updated to recommend weekly administration. Note that with oil-based anabolic steroids like the testosterones and Nandrolone Decanoate there can be a pool of the drug that accumulates in the injection site area that lengthens the decline in blood levels somewhat after several injections. Still, after observation many people over the last several years, It has been noted that for most consistent blood level of the drug and best overall patient quality of life, weekly administrations work best.
