A steroid is a chemical substance derived from cholesterol.
Catabolic steroids break down tissue, and anabolic steroids build up tissue.
Anabolic steroids build muscle and bone mass primarily by stimulating the muscle and bone cells to make new protein. Athletes use anabolic steroids because they increase muscle strength by encouraging new muscle growth. They allow the athlete to train harder and longer at any given period. In females, the excessive concentrations cause male characteristics to develop and interfere with normal female functions. When inhaled, beta-2 agonists relax the smooth muscle in the airways of asthma patients by mimicking the actions of epinephrine and norepinephrine, substances that are secreted by sympathetic nerves.