Many performance-enhancing substances naturally occur in our own bodies. When supplemented by needle, cream, or pill, they enhance the properties of that innate material. However, if taken too often or at improper doses, the user can experience stroke, heart attack, liver damage, increased blood pressure and cholesterol, diabetes, acne, heart deformations, insomnia and, in some cases, death. According to clinically based journals, like PharmacyTimes.com, and anecdotal evidence, some of the most common PEDs abused in endurance sports are: