What is it? An anabolic steroid (a steroid that acts as the hormone testosterone) that occurs in small amounts in the human body.
Medical Use: Used to treat osteoporosis in postmenopausal women, to aid in the growth of blood cells in bone marrow, and to help tissue and muscle growth in people suffering from degenerative diseases like AIDS.
Athletic Use: To grow muscle mass and aid in physical recovery from workouts.
Possible Negative Side Effects: Cardiovascular damage, sexual dysfunction, liver damage, acne, sterility, baldness, enlarged prostate.
Is it legal? Available only by prescription.
Heavy consumption of the essential amino acid lysine (as indicated in the treatment of cold sores) has allegedly shown false positives in some and was cited by American shotputter C. J. Hunter as the reason for his positive test, though in 2004 he admitted to a federal grand jury that he had injected nandrolone.  A possible cause of incorrect urine test results is the presence of metabolites from other AAS, though modern urinalysis can usually determine the exact AAS used by analyzing the ratio of the two remaining nandrolone metabolites. As a result of the numerous overturned verdicts, the testing procedure was reviewed by UK Sport . On October 5, 2007, three-time Olympic gold medalist for track and field Marion Jones admitted to use of the drug, and was sentenced to six months in jail for lying to a federal grand jury in 2000. 
The Story: In February 2005 Canseco released his autobiography and steroid tell-all, Juiced , Wild Times, Rampant 'Roids, Smash Hits, and How Baseball Got Big. In it he described himself as 'the chemist' having experimented on himself for years. He claimed to have educated and personally injected many players including Mark McGwire, Rafael Palmeiro, Juan Gonzalez, Ivan Rodriguez, and Jason Giambi. In his second book, Vindicated , Canseco added Magglio Ordonez to the list of players he had educated and injected with steroids. He also said he introduced Alex Rodriguez to a trainer/PED supplier after Rodriguez had asked where he could get steroids.