Nandrolone decanoate, also known as 19-nortestosterone, is an injectable medication that belongs to the group of drugs called class II anabolic androgenic steroids (AAS). The drugs that fall under class II AAS are all known as 19-nortestosterone derivatives; they are all synthetic derivatives of the endogenous male hormone testosterone. The primary role of testosterone in the human male is to aid the development of secondary sexual characteristics (androgenic effects) during puberty and the development as well as maintenance of muscle mass (anabolic effects); drugs, such as Nandrolone decanoate, that fall under the AAS category were synthesized to have more anabolic and less androgenic properties.