There are constant debates and many studies arguing the potential side effects for a user. There are studies showing that GW-501516 has caused cancer in rats while other studies refute it. The ONE study that was conducted that showed this issue was deeply flawed and refuted time and time again. GW-501516 dosing was not only abused but ran at insurmountable amounts of time within this study. When ran properly, it has actually been used as a cancer treatment. There are no known side effects associated with GW use and the only need to cycle off is so that one’s body does not acclimate or desensitize to use. There is no suppression, no toxicity and no other common side effects. This makes GW even more desirable amongst the bodybuilding community.
In November 1942, the Italian cyclist Fausto Coppi took "seven packets of amphetamine" to beat the world hour record on the track.  In 1960, the Danish rider Knud Enemark Jensen collapsed during the 100 km team time trial at the Olympic Games in Rome and died later in hospital. The autopsy showed he had taken amphetamine and another drug, Ronicol , which dilates the blood vessels. The chairman of the Dutch cycling federation, Piet van Dijk, said of Rome that "dope – whole cartloads – [were] used in such royal quantities." 
"Steroid" is the name given to a chemical compound with a specific structure. In everyday speech, the term steroid is applied to several medications that share this structure; however, these medications have very different uses. Anabolic steroids are a class of drug that mimic the effects of male sex hormones called androgens which stimulate muscle growth and secondary male sex characteristics. They are often abused by bodybuilders and other athletes to build muscle mass and so should be used with caution. When prescribed, oral steroids should be taken as directed. If you come across extra pills that haven't been taken, and are unsure if they are steroids, you can identify the pill based on its physical appearance, information on the bottle, or by consulting a professional.