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UFC 187: What do the Belfort and Weidman testosterone test results tell us?

An attempt to look a little deeper into what science tells us about Vitor Belfort's urine test results for UFC 187 that champ Chris Weidman found "funny" and "crazy."

Vitor Belfort fields questions on UFC 187 media day
Vitor Belfort fields questions on UFC 187 media day
Esther Lin

Out of competition test results from Chris Weidman and Vitor Belfort have returned with some surprising results which have sparked comments from both Weidman and Belfort that you can read here. The results are strange, but perhaps not for the reasons Chris thinks.

Before discussing that, though, it's important to have at least a basic understanding of the test results and what they can, and cannot, tell us.

First, the caveats.

  1. Single urine tests for testosterone levels are notoriously unreliable. Generally for an accurate reading all urine over a 24 hour period is collected and tested. That doesn't seem to be the case here. That means the absolute levels of testosterone (3.7ng/mL x2 for Weidman, and 12ng/mL and 5ng/mL for Belfort) should be taken with a pinch of salt. Where spot urine tests can be useful is for T:E ratios. More on that later.
  2. We don't know what time of day these tests were taken (which can make a significant difference), what kind of physical exercise Belfort or Weidman had participated in prior to the test, whether they were taking opiate based painkillers, or any of a dozen other factors which can lower your testosterone levels temporarily.
  3. Reference values for testosterone and epitestosterone levels in urine a generally taken from 24 hour samples and converted into ng/mL. This is an imperfect system to say the least. Without knowing the actual reference values the lab has for spot tests, it's essentially impossible to draw any meaningful conclusions from the absolute values presented in the tests.

Now, onto the tests themselves. What stood out to me most was that Weidman's T:E ratio was 1:10 on two separate occasions, a month apart. A normal ratio is somewhere around 1:1, though 1:4 through 4:1 will occur in a small percentage of the population. To be completely clear, none of Weidman's other results suggest anything nefarious. This isn't a situation where his results are suspicious and suggest wrongdoing. They're just odd, and I'd hope he gets regular blood tests (which are much more accurate) to make sure nothing is amiss.

Here's the pertinent science regarding these tests:

Normal reference levels for testosterone in urine is about 60ng/mL, based on a published reference range of 9.7ng/mL to 109.7mg/mL (mean average 61.3) for T in urine. Range of 3.7 to 111.0ng/mL (45.8 mean) for epi. The caveat being those numbers seem to be derived from ug/24 hour levels and an assumption of 1l of urine per day.

This means that without baseline measurements, and without knowing the labs reference values, any definitive conclusion about these results would be completely speculative.

Blood test results are typically much more accurate and useful for measuring T levels and drawing any conclusions about absolute levels (as opposed to just a T:E ratio) from a urine test is shaky science at best.

In short, Vitor's results didn't come back with strangely high testosterone levels or T:E ratios.

The change in his testosterone between tests could be easily explained by a number of factors (see above). In fact, if anything they seem to be low. Weidman's numbers are even lower, however, which is strange, but not suggestive of any wrongdoing whatsoever. All of that being said, be very wary of anyone trying to draw strong conclusions from these results, as there is much missing information and even with perfect information, single urine tests are notoriously unreliable indicators of absolute levels of testosterone etc. Which is why blood samples are typically used in medicine instead.