Human Growth Hormone:

Formerly extracted from cadavers, now made synthetically. Untraceable in urine. Used legitimately by paediatricians for treatment of dwarfism. Misused by athletes for quick recovery and muscle growth. Can cause disfigurement by encouraging growth in bones as well as muscles.

Erythropoietin:

Drug of choice on Le Tour de France. Natural hormone. Stimulates growth of red blood cells. Now genetically engineered for treatment of kidney disease and anaemia. Creates red blood cells to carry oxygen to the muscles. Undetectable in urine. Prolonged use may turn blood to sludge. Cyclists who use the stuff extensively have to wear heart monitors which wake them up at night if their blood thickens. They have to jump up and work out on an exercise bike for 30 minutes to get things pumping again.

Insulin Growth Factor-1

Another naturally produced substance, draws nutrients into muscle tissue, promoting growth. Wide range of legitimate uses. In athletes it increases the anabolic response of skeletal muscle. Explainable in urine.

Stimulants:

Ephedrine, pseudoephidrine, phenylpropanolamine are the names you'll hear, but the category also includes cocaine, amphetamines, and caffeine. Increases alertness and improves blood flow. May produce headaches and high blood pressure. Generally available in cold treatment compounds which athletes are forever inadvertently taking. Detectable in urine.

Beta 2 agonists:

Halfway between a stimulant and an anabolic steroid. Used legitimately in treatment of asthmatic conditions. Clenbuterol is the most notorious of the grouping. Increases muscle mass and reduces body fat. Detectable in urine.

Testosterone:

Naturally produced but available synthetically since 1935, testosterone is the king of steroids. Ben Johnson made Stanozolol (Winstrol) the best-known brand, but nandrolone has its devotees. American slugger Mark McGwire has done much to popularise Androstenodione, a steroid which promotes the natural production of testosterone. Upside is breakdown of fat cells and increased aggression and strength. Risk of liver damage and androgenic effects are among the drawbacks. Detectable in urine, but as it is naturally occurring argument persists over the safeness of such cases.

Anabolic Steroids:

Category which includes testosterone and all substances related to it. General misuse in sport for improvement in muscle mass and bulk. Not good for the skin or the liver or your cardiovascular system, but may cause loss of breast tissue in women or shrunken testes in men. Detectable in urine but easily masked and with the doses well administered you shouldn't lose sleep over it.

Diuretics:

Eliminate fluid from the body. Used for removing fluids after heart failure and more commonly for reducing blood pressure. Used by athletes to make weight limits, to overcome fluid retention problems caused by steroids and to alter concentrations of banned drugs in urine.

Human Chorionic Gonadatropin:

A pregnancy hormone (produced by placental cells and used to treat infertile women) which when administered to males leads to an increased rate of production of natural anabolic steroids by the testes. Considered the equivalent of administering testosterone.