ByIain Kidd, writer at
Scottish writer and researcher of MMA, pharmacology, nutrition and more besides.
Iain Kidd

In light of Jon Jones and, allegedly, Brock Lesnar both failing USADA tests for a substance known as Clomiphene, Iain Kidd breaks down what exactly that is, and why a fighter would use it. Note that nothing in this article should be taken as confirmation that Brock Lesnar failed a drug test for clomiphene.

Clomiphene, or Clomid, is a fertility drug, usually prescribed to women who are having specific issues conceiving. It acts primarily on the "female sex hormone" estrogen, and it induces ovulation. Since male athletes don’t ovulate, why would they take clomiphene? Well, this is where biology gets interesting.

Clomiphene is a selective estrogen receptor modulator. In plain English, that means the drug blocks certain estrogen receptors in the body, preventing estrogen from being used by those receptors. One of the areas clomiphene in particular blocks is the pituitary, which give it some very useful properties for athletes.

Testosterone is the "male sex hormone," and it’s also the steroid. It would be fair to say testosterone is the primary determinant of a person’s muscle mass. Increasing testosterone is the goal of many a supplement and magic bean. You may have heard of "testosterone replacement therapy" or TRT in the past. TRT is injecting external testosterone to make more available to the body and the muscles.

Injecting testosterone is both easily detected by drug tests, and detrimental to the body. The more exogenous (external) testosterone the body has, the less testosterone it will produce naturally. This is why steroid abusers will present with hypogonadism (reduced sex hormone production) after abusing steroids. As a result the holy grail of performance enhancing drugs is increasing the body’s own natural (endogenous) production of testosterone.

Testosterone is produced in something called the HPTA system, or the Hypothalamic-Pituitary-Testicular Axis. Remember when I said clomiphene blocks estrogen’s action in the pituitary? Here’s why that matters; the pituitary releases luteinizing hormone, which is tells specific cells in the athlete’s body to produce testosterone. Estrogen acts as a signal to the pituitary to produce less luteinizing hormone. If you stop the estrogen from reaching the pituitary, you can double your body’s testosterone production, and that’s exactly what clomiphene does.

Clomiphene is also referred to, and used as, a post-cycle therapy or PCT drug. A cycle here refers to one of steroid use, which is typically six to eight weeks of taking steroids, followed by a period of PCT to return your body’s hormones to their normal levels.

When you take steroids, your testosterone levels rise, and through a process called aromatization, some of that testosterone is converted to estrogen. As a general rule, high levels of estrogen are undesirable in men. They lead to increases in subcutaneous fat, especially fatty breast tissue, and decrease natural testosterone production via the method listed above.

As a result, most steroid cycles are accompanied, at least part of the time, by a SERM such as clomiphene, and the SERM will be continued after the cycle as part of the PCT to help suppress the effects of estrogen and boost the natural testosterone production back to normal levels. Historically, clomiphene has been used alongside or after steroids. Using it as a way to increase testosterone on its own is an idea growing in popularity. Several studies supporting the use of clomiphene as a medical alternative to TRT for treating secondary hypogonadism already exist.

One of the major issues for any elite athletes looking to take clomiphene as a performance enhancing drug is its relatively long detection window. While some PEDs have detection windows measured in hours, clomiphene’s detection window is measured in weeks. While clomiphene is undeniably effective, it’s also a poor choice for any regularly tested athlete looking to take PEDs without being caught.

So why would an elite athlete take clomiphene? Because it’s a method of doubling testosterone with relatively few side effects compared to taking steroids, and because it helps the body recover from any prior steroid use in the event they have taken steroids in the past.

You can follow Iain Kidd on Twitter, where he occasionally tweets about fighter safety, weight cutting, PEDs and other MMA topics.

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