Nandrolone, also known as 19-nortestosterone, is an anabolic steroid. Like testosterone, it influences the development of the male sexual organs and the build-up of protein in the muscles. In the average man, the ratio of testosterone to nandrolone in the body is 50: 1. Since nandrolone has a much higher activity than testosterone and the relationship between virilizing effect and anabolic effect is shifted in favor of the metabolic effect, it is of greater interest as a doping agent. Trenbolone is a derivative of nandrolone.