Anabolic steroids increase the rate of protein synthesis within cells. The building of cellular tissue (anabolism) is especially noticeable in muscles.
Anabolic processes tend toward “building up” organs and tissues. These processes produce growth and differentiation of cells and increase in body size, a process that involves synthesis of complex molecules. Examples of anabolic processes include the growth and mineralization of bone and increases in muscle mass. Endocrinologists have traditionally classified hormones as anabolic or catabolic, depending on which part of metabolism they stimulate. The classic anabolic hormones are the anabolic steroids, which stimulate protein synthesis and muscle growth, and insulin.
Steroid hormones work by stimulation of receptor molecules in muscle cells, which activate specific genes to produce proteins. They also affect the activation rate of enzyme systems involved in protein metabolism, thus enhancing protein synthesis and inhibiting protein degradation (called an anti-catabolic effect).
Once ingested, an AAS travels through the blood stream to the muscle tissue. It is drawn into the muscle cell’s receiving dock, called an androgen receptor. Once delivered to the muscle cell, the steroid can interact with the cell’s DNA and stimulate the protein synthesis process that promotes cell growth.
Anabolic steroids increase protein synthesis in skeletal muscles and reverse catabolic processes. Because of these properties, some athletes use anabolic steroids in an attempt to improve their athletic performance. However, studies indicate that increases in muscle mass and strength during anabolic steroid administration are observed only in athletes who already are weight-trained and who continue intensive training while maintaining high-protein, high-calorie diets.
Even though in isolation, synthesized and actively experimented with for many decades now, and at this point the primary mode of anabolic action with all anabolic/androgenic steroids is to be a direct activation of the cellular androgen receptor and increase in protein synthesis. By supplementing external anabolic usage the increase of hormone levels, so does the androgen receptor activation, and finally the protein synthesis effect.
An indirect mechanism is one that is not directly brought about by activation of the androgen receptor. But the affect androgens might have on other hormones, or even the release of locally acting hormones or growth promoters inside cells. Muscle mass disposition involves not only protein synthesis, but other factors as well such as protein breakdown and tissue nutrient transport. In recent years insulin, a hormone that increases transport of nutrients into muscle cells. In which a second way of transport indirectly of protein breakdown to cause muscle growth.