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SERMs boost testosterone levels in men only

Doping experts knew it already, but it's always nice when their views are confirmed by science. Anti-oestrogens like clomiphene [the active ingredient in Clomid], tamoxifen [Nolvadex] and toremifene [Fareston] only boost androgen levels in men, not in women. Doping hunters from the Federazione Medico Sportiva report on the matter in Steroids.

The Italians' research was intended to clarify whether conventional doping tests for testosterone use were also capable of detecting clomiphene, tamoxifen and toremifene. These three substances are selective oestrogen receptor modulators, or SERMs. They attach themselves to the estradiol receptor, but only activate some of the processes that estradiol initiates. At the same time they hinder estradiol in doing its work.

Clomid [below left] and tamoxifen [centre in figure below] have been on the market for a while; toremifene [below right] is a relative newcomer. Toremifene probably has fewer side effects than the other SERMs. Chemical athletes who make long-term use of SERMs often complain of reduced libido, and sometimes also of stiff or even painful joints. You rarely hear these complaints from toremifene users.

SERMs boost T levels in men only

On the web there are even stories from toremifene users whose libido has increased. "It relieves my prostate, it increases my libido extremely fast, gives me a porn-star load, it clears my acne and most importantly, at a high enough dose (120-150 mg) it gives me the typical dianabol feel good", writes one user on the CEM-forum. [ 12-18-2010]

In the brain SERMs have an anti-estrogenic effect. They kid the hypothalamus into thinking there are fewer sex hormones circulating in the blood, and as a result the gland secretes more GnRH hormone. This induces the pituitary to produce more LH, and this hormone stimulates testosterone production in the testes.

At least, that's how it works in men. But does it also work like this in women? No, say the researchers.

The Italians gave several male and female test subjects aged between 25 and 43 at 0 hour a dose of 80 mg tamoxifen, 100 mg clomiphene or 120 mg toremifene. At 24 hour they repeated the procedure.

The figure below shows the effects of the toremifene intake on the male subjects' urine. Their testosterone concentration had risen. The mutated clover indicates where there was a statistically significant rise.

SERMs boost T levels in men only

SERMs boost T levels in men only

The testosterone concentration didn't rise in the women who had been given toremifene, as the figure above shows.

The researchers observed the same effects when they tested for clomiphene and tamoxifen. After thirty hours the men's testosterone level had risen; that of the women had not.

The first thing that doping hunters look at is the relationship between testosterone [T] and epitestosterone [E] to see whether someone has used synthetic testosterone. If someone shows high levels of testosterone in the urine, then he's a suspect if the epitestosterone levels are low. That's why clever chemical athletes mix a little epitestosterone in with their testosterone to keep the T/E ratio constant. But if you use a SERM, it's not necessary to use epitestosterone. SERMs boost the synthesis of testosterone and epitestosterone by similar amounts.

By the way, doping tests for the three SERMs are already around. The Italians recently published one for toremifene. [Anal Bioanal Chem. 2011 Aug; 401(2): 529-41.] It was the first of its kind. We have no idea whether it's in use yet.

Steroids. 2011 Nov;76(12):1400-6.

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