Nandrolone undecanoate (brand names Dynabolon) is an anabolic androgenic steroid (AAS), which had been used for the treatment of the anemia of chronic renal failure for more than 25 years. Due to concerns over adverse effects, their use historically has been limited to nandrolone decanoate given to men, usually over age 50, who have intact kidneys. It binds to the androgen receptor to a greater degree than testosterone, but due to its inability to act on the muscle in ways unmediated by the receptor, has a less overall effect on muscle growth. Despite the fact that AAS are banned substances by professional sports organizations and illegal drugs by the DEA, they are used and abused extensively, especially by teenagers and young athletes or non-athletes either for cosmetic or recreational purposes. Users may even take from 10 to 100 times higher doses than the physiological one.