Anabolic steroids. A vial of testosterone and a syringe next to a towel and training shoes. Testosterone, the male sex hormone, is sometimes abused by athletes for its protein-building (anabolic) effect. Like synthetic anabolic steroids, which are based on testosterone, it speeds up muscle recovery after exercise, increasing muscle bulk and allowing a more intensive training schedule. Side-effects include increased aggressiveness, liver damage, oedema (fluid retention), acne, impotence, priapism (persistent, painful erection) and virilization in women. Anabolic steroids are banned in sport.