Epitestosterone is a male steroid hormone very similar in molecular structure to testosterone. Males and females produce this hormone naturally when testosterone is metabolized. Large doses of it have been used to cover up the illegal use of other steroid hormones in professional athletics. The normal result for the ratio of epitestosterone to testosterone in the body is close to 1:1. Olympic athletes must stay under a 4:1 limit, and professional football players must be under a 6:1 ratio to avoid being penalized.
Some people take anabolic steroid hormones to improve their athletic performance and to shorten the time it takes to build muscle mass. The excess steroid hormones can cause the overgrowth of body hair and also cause the voice to deepen in tone over time. A male may notice a decrease in the size of his testicular tissue as a result of anabolic steroid use. Athletes that take these steroids will need to disguise their use when tested.
The test to determine the ratio of epitestosterone to testosterone is performed on urine samples. A laboratory will do a gas chromatography to show the ratio of the two hormones. Much higher amounts of epitestosterone than testosterone generally indicate an artificial use of anabolic steroid hormones, since the naturally occurring hormone is commonly injected to disguise the presence of steroids in the urine.
A more sensitive test called a high performance liquid chromatography/tandem-mass spectrometry (HPLC/MS) is sometimes used when the results of the first test are called into question. Some athletes have maintained a metabolism issue indicates a false positive, as opposed to the illegal use of steroids. The HPLC/MS is able to differentiate between masking the use of a steroid and a metabolic issue that may cause elevated levels of the natural steroid hormone.
Use of epitestosterone is not proven to increase muscle mass or improve athletic performance. It is an inactive epimer of testosterone, and is usually injected to hide the use of anabolic steroids. The natural steroid is not metabolized by the hepatic or renal system, and therefore has very little effect on the healthy body.
Naturally produced large doses of epitestosterone have not been shown to have any adverse side effects. Levels of the steroid hormone stay consistent throughout middle adulthood. Most adolescents have the highest level of epitestosterone when tested. The amount of the hormone naturally produced by the body will decrease with age, as testosterone production decreases.
A few supplement companies sell a cream made of epitestosterone and testosterone. The cream is applied to the skin to allow the steroid hormones to pass through the epithelial tissue. It was designed to be less detectable in urine tests, allowing for its use among those that are regularly tested for performance enhancing substances.