To strengthen the anabolic properties of testosterone, more than 100 synthetic steroid derivatives have been described for human purposes. The anabolic effect promotes protein synthesis, muscle growth and erythropoiesis. In clinical practice, substances with anabolic effect are needed to overcome various catabolic states. However, none of these compounds are devoid of androgenicity. Androgenic and anabolic properties of anabolic steroids cannot be totally separated. Therefore, it is more appropriate to use the term anabolic androgenic steroids (AAS).
Transdermal patches (adhesive patches placed on the skin) may also be used to deliver a steady dose through the skin and into the bloodstream. Testosterone-containing creams and gels that are applied daily to the skin are also available, but absorption is inefficient (roughly 10%, varying between individuals) and these treatments tend to be more expensive. Individuals who are especially physically active and/or bathe often may not be good candidates, since the medication can be washed off and may take up to six hours to be fully absorbed. There is also the risk that an intimate partner or child may come in contact with the application site and inadvertently dose himself or herself; children and women are highly sensitive to testosterone and can suffer unintended masculinization and health effects, even from small doses. Injection is the most common method used by individuals administering AAS for non-medical purposes.