Driada medical "Nandrolone" (chemical name - 19-nortestosterone) - an anabolic steroid can be formed in the human body after heavy or prolonged physical effort or during pregnancy, the concentration of its main metabolite 19-norandrosterone in urine , but in very low concentrations. Structurally, nandrolone differs from testosterone in the absence of a carbon atom in the 19th position (hence the name 19-nortestosterone) and this makes it more similar to progestins. Due to its progestin origin, nandrolone exhibits significantly less androgenic effect compared to testosterone, however, stabilization of progesterone receptors causes an unique side effects. Another difference is that unlike testosterone, that converts by the enzyme 5-alpha reductase into a powerful androgen - dihydrotestosterone, which is responsible for the development of most of the side effects. On the contrary, Nandrolone, is converted by 5-alpha reductase into an extremely weak androgen – dihydronandrolone.