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E number{{#property:P628}}
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Chemical and physical data
Molar mass288.42

Epitestosterone is a natural steroid, an inactive epimer of the hormone testosterone. Structurally, it differs from testosterone only in the configuration at the OH-bearing carbon, C17. Epitestosterone is believed to form in a similar way to testosterone; a 1993 study found that around 50% of epitestosterone production in human males can be ascribed to the testis,[1] although the exact pathway of its formation is still the subject of research. It has been shown to accumulate in mammary cyst fluid and in the prostate.[2] Epitestosterone levels are typically highest in young males; however, by adulthood, most healthy males exhibit a testosterone to epitestosterone ratio (T/E ratio) of about 1:1.[3]

Epitestosterone and testosterone

It has been shown that exogenous administration of testosterone does not affect levels of epitestosterone in the body. As a result, tests to determine the ratio of testosterone to epitestosterone in urine are used to find athletes who are doping.[4] Most persons have a ratio of about 1:1 testosterone to epitestosterone (T/E ratio) in their urine. However, it is not uncommon to find T/E ratios of up to 4:1 and even T/E ratios of 10:1 can be normal for some individuals. T/E tests are most common because a person may naturally have high levels of testosterone, but even so T/E ratios tend to stay close to 1:1.

Epitestosterone has not been shown to enhance athletic performance, although administration of epistestosterone can be used to mask a high level of testosterone if the standard T/E ratio test is used. As such, epitestosterone is banned by many sporting authorities as a masking agent for testosterone.

In 1996 the US athlete Mary Decker failed a T/E test with a T/E ratio of greater than 6, the limit in force at the time. She took the case to arbitration, arguing that birth control pills can cause false positives for the test, but the arbitration panel ruled against her.

On September 20, 2007 Floyd Landis was stripped of his title as winner of the Tour de France, and was subjected to a two year ban from professional racing after a second test showing an elevated T/E ratio. Test results from Floyd Landis' "A" test sample indicated that while the ratio was 11:1, his testosterone level was in the normal range and the problem was actually a deficient level of epitestosterone. Landis won the 17th stage of the tour; however, tests taken immediately after the stage victory showed a T/E ratio of 11:1[5], more than double the 4:1 imposed limit (recently lowered from prior limits of 8:1 and 6:1). Landis had emphatically denied the charge, pointing out the scientific data that testosterone cannot enhance athletic performance unless taken over an extended period of time with regular doses.

External links


  1. "Secretion by the human testis of epitestosterone". The Journal of steroid biochemistry and molecular biology. 1993 Feb;44(2):171-7. Check date values in: |date= (help)
  2. "Secretion by the human testis of epitestosterone". The Journal of steroid biochemistry and molecular biology. 1993 Feb;44(2):171-7. Check date values in: |date= (help)
  3. "Characterization of 17α-hydroxysteroid dehydrogenase activity (17α-HSD) and its involvement in the biosynthesis of epitestosterone". BMC Biochemistry 2005, 6:12. 14 July 2005.
  4. "Detection of Epitestosterone Doping by Isotope Ratio Mass Spectrometry". Clinical Chemistry. 2002;48:629-636. Check date values in: |date= (help)
  5. This is disputed. According to testimony offered in the USADA hearing, multiple test of the same sample produced results ranging from 4:1 up to 11:1. The lab chose to report the 11:1 figure.

da: Epitestosteron de: Epitestosteron