Hormones - How Do Testosterone Precursors & Steroids Work?

Testosterone Precursors

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So many products claim to increase androgenic hormones. How do these testosterone precursors and steroids work? Surely you've come across and heard a lot of different info on this.

Unfortunately, there are many misconceptions about how androgens make muscles grow. With all this BS around, it's important to have some information on how steroids really work. Here's an update on the latest scientific findings.

To gain a working knowledge of androgen action, we need to travel to the cellular level. Imagine a steroid molecule as a key floating through the bloodstream. This key fits into a lock (a receptor) and, once the hormone is bound to a cell in this way, all sorts of activity goes on in the cell. One of these cellular events is protein synthesis.

Receptors are located all over the body, but the ones we're concerned with are in muscle. Muscle serves as a primary target tissue for androgens circulating in the bloodstream.

Believe it or not, when athletes first started using androgens, most scientists did not believe they worked. In fact, understanding how steroids induce anabolism in muscle has been one of the great mysteries of science, until recently. The androgen receptor (AR) in human muscle was located in 1981, when a group of Swedish and Polish scientists identified its presence in the quadriceps.

Data shows that, at normal physiological levels, the ARs are completely saturated. With all the receptors supposedly filled, scientists mistakenly thought that additional steroids introduced into the system would be unable to effect changes on muscle growth. (Were they wrong!) Also adding to the argument that steroids had no influence on muscle size was the belief that the AR down-regulates (stops working) after a guy goes through puberty. Therefore, it followed that there were no ARs upon which the androgens could act. But the latest studies on 'roids show that they can work outside of the receptor complex.

Studies have also shown that certain steroids have what is called a high binding affinity. Greater binding increases the possibility that the steroid will be able to exert its effects on muscle. One study found that 19-nortestosterone derivatives (trade names Deca-Durabolin and Laurabolin), methenolone (Primobolan) and testosterone all have a high binding affinity.

What's surprising is that some of the more popular steroids among athletes have a low binding affinity for the AR. Those showing low binding ability are stanozolol (Winstrol), methandrostenolone (Dianabol, Reforvit-B) and fluoxymesterone (Halotestin, Stenox). Interestingly, though these steroids don't bind to the AR very well, they are some of the most effective drugs for muscle building. That means some steroids might be using other pathways to exert their effects on protein synthesis, namely, the insulinlike growth factor-1 (IGF-1) system. Also, how big a role binding affinity plays in humans using large dosages should be further examined.


IGF-1 is one of the most potent anabolic agents produced by the body. Studies have shown that taking testosterone increases IGF-1 levels dramatically; other steroids, namely Deca, decrease levels of a protein that binds IGF. If you , lower the levels of binding protein, you raise the levels of free or active hormones. The result is that more hormones can interact with muscle and, you guessed it, produce a greater growth response.

Frequently, the actions of a drug, have a multitude of effects. Such is the case with steroids. Androgen action is an extremely complex chain of events, and we now have to add another variable to the list.

The body's own defense mechanism for stress, and every bodybuilder's worst nightmare, is Cortisol. Cortisol breaks down muscle tissue, thus preventing muscular growth (a.k.a. anabolism). If you block the effects of this potent muscle-dissolving hormone, you're well on your way to growing bigger muscles. Enter anabolic steroids.

Some scientific research has revealed that androgens deter cortisol-associated muscle loss. I say some, because not all studies prove this effect. Though the scientific literature is not consistent, most experts will tell you that, at high dosages, androgens do interact with the receptors for Cortisol.

It's also been shown that with resistance training, type-II (fast-twitch) muscle fibers up-regulate (turn on) more androgen receptors. As guys get bigger from lifting weights, then, they might actually be gaining androgen receptors.


As we've noted, the anabolic consequences of steroid hormones on the human body are extremely complex. Steroid drugs possess the unique ability to change the function of almost every tissue in the body. These actions can produce any number of problems, from the superficial (e.g., acne, gynecomastia) to the very serious (inhibited organ function). Of course, steroids are illegal, but over-the-counter testosterone precursors and other supplements can - if taken in quantity - also produce negative side effects. Whatever you do - or take - keep learning and stay healthy.

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