How Steroids Work In Building Muscle Mass
Anabolic steroids and how they can promote muscle growth

A steroid is a chemical substance that originally comes from cholesterol. The body has several major steroid hormones. Cortisol and testosterone are the dominant hormones in the male, while estrogen and progesterone are the dominant hormones in the female. Catabolic steroids break down tissue, and anabolic steroids build up tissue. Anabolic steroids build muscle and bone mass mainly by stimulating the muscle and bone cells to produce new protein.
Athletes use anabolic steroids because they are reputed to increase muscle strength by encouraging new muscle growth. Anabolic steroids are very similar in structure to the male sex hormone, testosterone, so they enhance male reproductive and secondary sex characteristics (testicle development, hair growth, thickening of the vocal cords). They allow the athlete to train harder and longer at any given period.
Anabolic steroids are mostly testosterone (male sex hormone) and its derivatives. Examples of anabolic steroids include testosterone, Dihydrotestosterone, Androstenedione (Andro), Dehydroepiandrosterone (DHEA), Clostebol, and Nandrolone.
These substances can be injected or taken as pills. Anabolic steroids have a number of possible and well-known side effects, including jaundice and liver damage because these substances are normally broken down in the liver, and frequent mood swings, depression and aggression because they act on various centers of the brain
In males, taking too much steroids can interfere with normal sexual function and cause baldness, infertility, and breast development
In females, taking too much steroids may encourage male characteristics to develop and interfere with normal female functions. The drugs can stimulate hair growth on the face and body, suppress or interfere with menstrual cycle, possibly leading to infertility, thicken the vocal cords, which causes the voice to deepen, possibly permanently, and, if pregnant, cause harm to the unborn fetus.

There are several different types of steroids athletes use to achieve different results. Here are a few:

Beta-2 Agonists – these steroids are typically used for asthma patients by smoothing muscles in the airways. However, when injected directly into the bloodstream, these drugs can build muscle mass and reduce body fat. Side effects include headaches, nausea, dizziness, and rapid heartbeat.

Human Chorionic Gonadotropin – this is a hormone produced by the developing fetus. It stimulates development of natural hormones in males and females. This stimulates muscle development in males and does not cause muscle development in females. 
Luteinizing Hormone – this is a peptide hormone secreted by the pituitary gland. This hormone would increase testosterone levels in men and cause similar effects of anabolic steroids.

Human Growth Hormone – this is a naturally occurring protein produced by the pituitary gland and an excess level of this hormone increases muscle mass and strengthens bones by stimulating bone growth and reducing body fat.