On March 12, 2004, the Anabolic Steroid Control Act of 2004 was introduced into the United States Senate. It amended the Controlled Substance Act to place both anabolic steroids and prohormones on a list of controlled substances , making possession of the banned substances a federal crime. The law took effect on January 20, 2005. However, androstenedione was legally defined as an anabolic steroid, even though there is scant evidence that androstenedione itself is anabolic in nature. On April 11, 2004, the United States Food and Drug Administration banned the sale of androstenedione, citing that the drug poses significant health risks commonly associated with steroids. Androstenedione is currently banned by the . military . 
In February 2009, Sports Illustrated reported that Alex Rodriguez tested positive for two anabolic steroids , testosterone and metenolone enanthate, while playing for the Texas Rangers in 2003. He claims to have purchased them over the counter, in the Dominican Republic . However, " boli ," as he referred to it, is an illegal substance in the Dominican Republic.   In an interview with ESPN two days after the SI revelations, Rodriguez admitted to using banned substances from 2001 to 2003, citing "an enormous amount of pressure to perform," but said he had not since then used banned performance-enhancing substances.   He said he did not know the name(s) of the particular substance(s) he was using, and would not specify whether he took them in injectable form. 
For example, anabolic steroids such as Testosterone have a tendency to promote water retention through their ability to be aromatized into Estrogen via the aromatase enzyme. While such an effect might not be a concern for a strength athlete or a powerlifter (such an effect might even be beneficial or desired in such sports), this is not a desired effect for athletes involved in sports that involve speed and swiftness, such as sprinting. Instead, a sprinter, for example, would more likely opt for an anabolic steroid such as Stanozolol ( Winstrol ) or Oxandrolone ( Anavar ), which are two anabolic steroids unable to convert into Estrogen and therefore the issue of water retention, and therefore the issue of added weight that would slow the athlete down is avoided. Many athletes may also elect to ‘stack’ anabolic steroids in a given cycle (stacking refers to the practice of combining more than one anabolic steroid in a cycle). In the case of cycle stacks, an individual might be able to increase the synergy and synergistic effects between the anabolic steroids to create a highly anabolic environment or to create a stack that might assist the user in favoring certain particular athletic or physique goals. These are some of the major reasons as to why the development of different types of steroids has been done.