The main androgen focused upon for this discussion is testosterone. But please realize that almost all synthetic AAS are chemical variants of testosterone and therefore much of the characteristics apply to them as well. (But not all!) Testosterone has two distinct characteristics or effects.

First, its anabolic characteristics (tissue building) which express themselves as increased and accelerated muscle tissue build-up which leads to faster recovery time after training- illness, and injuries, and to a quicker "regeneration" (I hate that word!) of the entire body. This is because an anabolic response leads to the promotion of protein synthesis and tissue repair or increase.

Secondly, androgenic characteristics or effects which are commonly referred to as secondary male characteristics that promote sexual behavior, libido, development and maturing of the penis, body hair, beard growth, deeper voice, aggressiveness, and formation and maturation of sperm. And of course, as any pubescent boy will tell you. increased production of the sebaceous gland and pimples.

As mentioned before, circulatory levels of testosterone also effect HPTA function, so I should not list it as a characteristic unless I also list pretty much every other sex-hormone as well.

When discussing the characteristics of testosterone or its androgen cousins and synthetic AAS relatives, it is important to understand the difference between free (or active) testosterone and bound (or inactive) testosterone/AAS (Anabolic/Androgenic Steroids). Bound testosterone is inactive because it is bound to SHBG (Sex Hormone Binding Globulin) and to a lesser degree, albumin. The sex-steroid molecules are bound by SHBG contained in the blood, which prevents them from fitting into their receptors. That will be explained later. Free (unbound/active) testosterone is able to transmit its characteristics because it fits into receptors. Bound testosterone equals about 97-99% of total testosterone circulation while free testosterone equals 1-3% of total testosterone.

That probably does not sound like much, but even 0.1-0.3 mg of free testosterone has a whole lot of individual separate molecules. And 1 molecule can activate every receptor-site it binds to. Males have a total testosterone reference range of 225-950 ng/dl (nanograms per decaliter). And a free testosterone reference range for males is 1-3% of the total testosterone reference range. Females have a total testosterone reference range of 14-76 112/dl and a free testosterone reference range of 0.5-1.8 ng/dl.

Bound testosterone can be unbound due to metabolic requirements and different steroid molecules. And both endogenous and exogenous AAS can react differently to SHBG. For this reason some synthetic AAS can alter the ratio for any other free and/or bound androgenic levels.

Most steroid molecules are specific to their respective cell receptors. This means only testosterone/androgen/AAS molecules can fit into (and transmit their respective message) testosterone/androgen receptor-sites. This is due to shape and size much like a key and a lock: Some keys can fit into other locks, but only the right key can fit in and activate the mechanism. Steroid molecules travel through the blood stream and lymphatic system. This means that everywhere blood goes, the molecules are sure to follow. Using muscle cells as an example, testosterone molecules circulate until they come into contact with testosterone/androgen receptor-sites on the muscle cell. Then they lock together and they form a complex called (what else?) a steroid / receptor complex. Now the complex travels to the cell nucleus where it can bond to specific sequences on the nucleic acid sections of desoxyribonucleic acid (DNA). Here is where a transcription happens and a template of the DNA is created, resulting in messenger ribonucleic acid (mRNA). The mRNA exits the cell nucleus and bonds to/with RNA in the liquid part of the cell called the cytoplasm. Here a translation of the message takes place and an increase in protein synthesis occurs. There is a correlating decrease in catabolism as well. This is because testosterone molecules can occupy Cortisol receptor-sites and block them. Therefore Cortisol can not get in to transmit its message. The results are growth! A simple way of looking at this is... you go to someone's house to deliver a message and their mom relays it exactly so the job gets done. Sony about the techno-geek info, but it helps later.

Technorati Profile