Anabolic/androgenic steroids (AAS), when introduced into the body, do not necessarily remain unchanged. Enzymatic processes often convert them to different molecules. This is true of the prohormones as well: androstenedione will not necessarily remain as androstenedione, but some of it will be converted to testosterone. Although that example is well known, many other enzymatic conversions of steroids are less well-known in bodybuilding. We will be looking at these conversions in this article.
Anabolic steroids given by intramuscular injection are usually (not always) esterified versions of the parent drugs (Figure 1). This esterification improves the oil solubility of the steroid, and reduces water solubility: the result is that the esterified drug remains stored mostly dissolved in fat, and the parent drug is released to the bloodstream only slowly, over time.
The enzymes that accomplish this transformation are called esterases, and are widely present in the body. Aside from allowing use of esterified drugs, they have another effect: they can also work in the reverse direction. Instead of removing an ester from the esterified drug, they can add an ester to the parent drug. This can increase the lifetime of the drug in the body. Thus, it could be expected that some small amount of a norandro prohormone would be converted to an esterified form, and would remain (in trace amounts) in the system for quite some time. Unfortunately, analytical techniques today are sufficient to detect nandrolone or its metabolites in extremely low concentrations. Thus, the norandro products cannot be recommended to anyone who might be subject to drug testing for AAS.
Esterases cannot work well on steroid esters that are 17alpha alkylated, because the alkylation blocks the approach of the enzyme to the ester. This is the reason that no such drugs are sold – there are no esters of Dianabol, methyltestosterone, Anadrol®, oxandrolone, Winstrol, etc., and there never will be (Figure 2). They would be inactive.
3beta hydroxysteroid dehydrogenase (3bHSD)
This enzyme, like the esterase enzymes, can work in two directions. It can either convert a steroid that has a keto group on position 3 of the steroid (Figure 3, the left molecule) to one with a hydroxy group in the same position (Figure 3, the molecule on the right) or vice versa. The latter action is seen when androdiol is converted to testosterone by this enzyme. The former is seen when DHT is converted to androstanediol (not androstenediol) in muscle tissue (Figure 4): this is the reason DHT is not an effective anabolic in muscle tissue.) Proviron also undergoes this transformation and is deactivated in muscle tissue (Figure 5).
The conversion of DHT to androstanediol also occurs in scalp tissue, and androstanediol may be of relevance in the development of male pattern baldness.
Because the enzyme works in two directions, it cannot convert a keto steroid entirely to the hydroxy, or vice versa, because some of what is converted will then be acted upon again and return to its original state. Thus, there will always be a mixture of the two compounds. In some cases, the mixture might favor one side of the balance.
3bHSD is widely distributed in the body.