Epitestosterone (epitest) is a natural steroid found inside the body, and it is an inactive epimer of testosterone (steroid hormone found in humans and vertebrates). In younger adults, epitestosterone is found at high levels, and in most healthy adult males the ratio of epitestosterone to testosterone in the body is about 1:1, but it can slightly vary based on race factors.

Epitestosterone has been used as a masking agent by athletes to hide their hormone use and fool doping tests.

testosterone vs epitestosterone

Fig 1. Testosterone vs Epitestosterone

Table of Contents

Epitestosterone vs. Testosterone

According to medical journals, the only structural difference between epitestosterone and testosterone is the configuration of the OH-bearing carbon, which is C17.

Both of these hormones are formed in the same way by the body, and production in human males comes from the testis. In spite of the fact that we still do not know epitestosterone's exact pathway, we do know that it accumulates in the prostate and the mammary cyst fluid.

Epitestosterone Functions

Based on rat studies, it is assumed that epitestosterone exists as a regulator of such androgen dependent events as body hair and prostate growth. As mentioned, it has no correlation with testosterone in the body. Therefore, injecting testosterone does not suppress epitestosterone and vice versa. That means the levels of testosterone do not affect those of epitestosterone. This is why epitest is such a great masking agent.

How it works

At this point, we can probably figure out how using epitestosterone works at masking testosterone. You simply would have to take enough to make your urine test look as close to 1:1 ratio as possible to avoid detection.

The athletes accused of doping could have avoided being caught if they used epitestosterone to make the ratio closer to 1:1. Unfortunately though, sporting authorities have wised up and banned the use of epitestosterone because of its masking abilities.

Epitestosterone in no way is a performance enhancing drug. It will not bring such properties of testosterone as increased strength, stamina, and mass.

How Epitestosterone dopers are caught

With urine doping tests, the administrator will determine if the athlete is doping or not by searching for imbalances between the ratio of epitestosterone and testosterone. As it was mentioned before, a normal adult male has a 1:1 ratio. However, a study of Australian athletes showed that their natural testosterone:epitestosterone ratios was slightly higher, being 1.15:1 on average. Furthermore, the ratio among the top 95% and then top 99% reached up to 5.25:1.

According to WADA, the test will be positive if the urine concentration is higher than 200ng/ml of epitestosterone.

The key to using epitestosterone as a masking agent is by fooling the doping tests into thinking your hormone levels and ratios are normal. Therefore, it is no surprise that some athletes who have been busted insisted on their innocence, since it is plausible that they unfortunately fell into that small percentage and were telling the truth. The bright side is that WADA will conduct additional tests to determine an athlete's fate.

Athletes who have been caught based on ratio

Two of the most well known athletes were runner Mary Decker, and bicyclist Floyd Landis who was stripped of his Tour de France win. Mary's ratio was 6:1 and Landis' was 11:1. The maximum allowed among bicyclists is 4:1, which covers over 95% of athletes according to the Australian study.

It is important to note that since he tested positive, Landis has admitted he did use PED's during his bicycling prime.

floyd landis epitestosterone

Fig 2. Floyd Landis Caught with abnormal ratios

Side effects

Side effects are non-existent with epitestosterone.


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