A synthetic, anabolic steroid hormone analog of testosterone. Similar to testosterone, oxandrolone binds to and activates specific nuclear receptors. This agent may be used for testosterone replacement therapy in hypogonadal men, in HIV-wasting syndrome, and in other conditions in order to increase nitrogen retention and fat-free muscle mass. or A chemical reaction that takes place between an oxidizing substance and a reducing substance. The oxidizing substance loses electrons in the reaction, and the reducing substance gains electrons. For example, rust forms when there is an oxidation-reduction reaction between oxygen contained in water or moist air (an oxidizing substance) and iron (a reducing substance). Oxidation-reduction reactions also occur when glucose (a type of sugar) and fat are broken down in the body to make energy. Also called redox.