Elite athletes start training when they are very young and often start taking drugs before they have the maturity to understand that they could be ruining their lives forever. Some are given no choice. According to the USADA here are just
some of the side effects of performance enhancing drugs:
http://www.usada.org/substances/effects-of-performance-enhancing-drugs/
Steroids: liver damage, premature closure of the growth centers of long bones (in adolescents) which may result in stunted growth, stunted growth and disruption of puberty in children, increased aggressiveness and sexual appetite, sometimes resulting in abnormal sexual and criminal behavior. Withdrawal of use can lead to depression & in some cases suicide.
Peptide Hormones, Growth Factors, and Related Substances: hypertension, blood cancers/leukemia, Anemia, strokes, heart attacks, Pulmonary embolism, thyroid problems, Severe headaches, Loss of vision, High blood pressure and heart failure, Diabetes and tumors, Acromegaly (Protruding or enlarged jaw, brow, skull, hands and feet), Crippling arthritis.
Blood doping: Increased stress on the heart, blood clotting, stroke