Anabolic steroids are synthetic versions of testosterone that users inject, ingest or apply to their skin in order to increase the amount of testosterone in their bodies.

Testosterone, primarily a male sex hormone, is naturally produced in the body by both men and women. In males, it is responsible for the growth and development of sex organs and also the maintenance of secondary sex characteristics (for example facial hair and bone growth). In females, it helps maintain bone density and muscle mass.