From Lawnsaver @ Steriodology

Biological Effects of Anabolic Steroids

Hormones are organic compounds synthesized in one location and targeted to another, causing specific biological changes in the organism. They attach themselves to receptor sites on the surface of the cell, which causes several responses in the plasma membrane and cytoplasm. The hormone binds to a receptor, which activates a G-protein in the plasma membrane. The G-protein activates an effector, also in the plasma membrane, which, in turn, causes a 2nd messenger to carry out one of three things:

Phosphorylating an enzyme to make it active or inactive,
Dephosphorylating an enzyme also activating or inactivating it, or
Opening ion channels to activate or deactivate an enzyme.
Enzymes are proteins that will carry out the reaction. Steroid hormones work in a different way.

Instead of going through the process by which ordinary hormone receptors cause several other agents to lead the hormone into the cell, steroid hormones diffuse across the plasma membrane into the cytoplasm. It enters the nucleus and binds to receptor proteins. This causes the release of an inhibitor protein from the receptor and allows the activated receptor protein to attach itself to genes on the DNA, which will lead to protein synthesis in muscle cells.

Athletes, or others interested in weight training, are consistently wanting to gain mass (mostly consisted of muscle) and enhance performance as a result to the increase in muscle. They want something that will increase protein production to build their muscles. Anabolic steroid hormones, upon attachment to the DNA, cause gene expression of RNA’s and transcription of proteins from those RNA’s. More protein leads to more muscle.

Recent studies show that anabolic steroids also cause the transcription of certain proteins called coactivators. Coactivators are said to connect the receptor protein, which is bound to the DNA, to the proteins that help initiate transcription, or transcription factors. This enhances protein transcription, as upon connection, these transcription factors activate RNA-polymerase to transcribe proteins from the RNA.

Besides causing an increase in protein production, anabolic steroids also have other effects on the body. After long periods of weight training, the body naturally gets tired, caused by an increase in levels of cortisol, another hormone produced in the adrenal cortex. Steroids reverse those effects by removing the cortisol from its receptors, allowing the athlete to continue training at high levels for longer periods of time. Additionally, anabolic steroids stimulate the release of the growth hormone, which will also lead to more mass and a bigger body. They also contribute to the increase in production of testosterone. This will lead to aggressive behavior which also allows more intense training sessions

If an athlete stopped taking the steroids, the size and strength gains would disappear rapidly. The motivational effects of the steroids are taken away not allowing the subject to train for long and intense periods. Testosterone levels drop and cannot maintain the heightened masculinity. This sometimes leads to a long-term abuse of steroids just to suppress these effects.