Testosterone: Like other hormones, testosterone is produced by both men (primarily in the testes) and women (in the ovaries) -- though the average man produces 10 times more than the average woman. Testosterone is classified as an androgen, or male sex hormone, because it promotes the development of masculine characteristics, such as body hair and a deep voice. It also has anabolic, or building, effects that can increase bone density and muscle mass.
Anabolic steroids: These are synthetic derivatives of testosterone that can be rubbed on, injected or swallowed. Athletes tend to inject them because oral steroids go through the digestive system and must be taken more frequently, making them harder on the liver. While some anabolic steroids have immense muscle-building power, no perfect steroid -- one without androgenic effects -- has been created since the hormone was initially isolated, in 1935. The first anabolic steroid widely distributed in the U.S. was Dianabol, developed by Olney, Md., physician John Ziegler in the late '50s. Ziegler, himself a man-about-gyms, created the drug to help American weightlifters compete with Soviets who were injecting testosterone.
Human growth hormone: The primary purpose of growth hormone, secreted by the pituitary gland at the base of the brain, is the maintenance of normal bone development from birth to adulthood. Synthetic human growth hormone, or somatropin, is typically used to treat growth disorders and the wasting effects of HIV/AIDS. Growth hormone is also involved in regulating the body's ratio of lean muscle mass to fat, and some athletes who inject it -- the molecule is too large to be absorbed into the bloodstream by other methods -- are able to tolerate a larger workout load. Athletes who use HGH often do so with anabolic steroids or testosterone, believing HGH adds to the anabolic effect. Because the amount of growth hormone in the body peaks during puberty and declines after age 30, those who illegally prescribe or sell HGH often claim that it counteracts the aging process.
Synthetic testosterone, anabolic steroids and HGH have bona fide medical uses, unlike street drugs such as heroin or cocaine. Doctors can legally prescribe many FDA-approved drugs, including testosterone, for uses other than those for which the drug was originally designed, but they are prohibited from prescribing steroids and HGH for off-label purposes, such as antiaging and athletic-performance enhancement. HGH is not a controlled substance under federal law, but steroids are; possession of them without a prescription is punishable by a prison sentence and a fine.
For testosterone: The average person has a 1-to-1 ratio of testosterone to the hormone epitestosterone. But people naturally have varying amounts of testosterone, so the World Anti-Doping Agency had to build flexibility into its policy. WADA considers a urine test positive only if the T-E ratio exceeds 4 to 1. Thus, some athletes try to boost their bodies' level of testosterone to just below the acceptable ratio.
For anabolic steroids: Steroids are generally taken to boost off-season workouts, which means antidoping programs that focus on in-season testing are doomed. In addition many steroids, particularly water-based, injectable ones, can largely clear the body in days, so testing must be frequent to be effective. Perhaps the most pressing problem for antidoping officials is designer steroids: They have customized molecular structures that keep their anabolic properties, but, because of their novelty, they're hard to detect with tests. BALCO gave athletes designer drugs, and it wasn't until Don Catlin, founder of the UCLA Olympic Analytical Laboratory, realized he was looking at a steroid not previously used for doping that he detected "the Clear."
For HGH: Most of the growth hormone molecules in an average person's body -- perhaps 80% to 85% -- weigh 22 kilodaltons each; the remainder come in other forms, including a 20-kilodalton variety. But synthetic HGH is composed entirely of 22-kilodalton molecules, so an athlete who has injected it will have an abnormally high percentage of those. A blood test for HGH is not yet commercially available, but antidoping officials expect one to be ready for Beijing.