Science Is Still Trying To Figure Out What Makes A Female Athlete

Sex tests in sports are archaic

Bicep Curl

Credit: OpenStax College via Wikimedia Commons

In 2013, professional sprinter Dutee Chand was banned from competing as a female athlete. She wasn't accused of doping, and she wasn't accused of not being a woman—she was born and raised as a girl. Instead, her hormones were at fault.

Chand's natural testosterone levels fall into a male range, and according to international regulations, she can't compete again until her testosterone lowers to a more ladylike level—a process that would require drugs or surgery. Chand refuses, and in March she challenged the ban. Switzerland's Court of Arbitration for Sport is expected to come out with a decision this summer.

A number of other female athletes have had their gender called into question as a result of the testosterone rules, most notably Caster Semenya, who had to undergo sex-testing after winning the women's 800 meter race in the 2009 World Championships.

According to regulations from the International Association of Athletics Federations (IAAF), female athletes' testosterone levels must be below the normal male range. The International Olympic Committee has similar regulations. In an opinion piece in Science, medical anthropologist Katrina Karkazis and her co-author explain that two scientific camps are duking it out over whether biology supports the controversial policy.

The testosterone limits are the latest attempt to draw a clear line between male and female athletes. In the old days, an elite female athlete would have to verify her sex through genital inspection or chromosome testing, but neither method was perfect. In the gray area between males and females, intersex people may have traits from both sexes. Policy-makers eventually gave up the idea of sex testing, ruling that people should be able to compete in the gender category that they identify with. Testosterone regulations, which came about in 2011 and 2012, are just a newer version of those older, flawed tests, Karkazis argues.

"Men have always been exempt from sex-testing," she tells Popular Science. "Historically, policy-makers thought men would masquerade as women. In the latest iteration, the rationale is that these women with high testosterone have unfair advantage."

To be clear, tests can reveal whether the testosterone in an athlete’s blood is natural or synthetic, so doping is not the concern. People like Chand have hyperandrogenism—their bodies overproduce male hormones.

But establishing the “normal range” of natural testosterone in elite athletes has been more difficult than expected. One study found that testosterone levels for male and female athletes overlap, with up to 13.7 percent of women having testosterone higher than the typical female range. A second study (conducted by IAAF researchers) showed that high testosterone levels were extremely rare in women, at 1.5 percent.

Neither study was perfect. The first one used a test that may have overestimated the women’s testosterone levels, but the IAAF study actually left out women with particularly high testosterone levels, thinking them to be outliers that would skew the data set.

Some athletes go under the knife to remove the hormone-secreting tissues.

In a way, the whole argument is moot since it’s not entirely clear that higher testosterone levels improve a woman’s performance. From the IAAF study: “there is no clear scientific evidence proving that a high level of T is a significant determinant of performance in female sports”.

What's more, if high levels of testosterone were really a performance concern, then shouldn't male athletes have a maximum as well? Karkazis' explanation is that "In men it doesn't blur a sex divide." Popular Science reached out to IAAF scientists for comment, but they did not respond in time for this article.

Asking someone to lower her testosterone is no light request. “The body is like an ecosystem—you change one thing and everything else changes,” says Karkazis. “A whole bunch of other hormone changes get triggered.” To meet the IAAF criteria, some women go under the knife to remove the hormone-secreting tissues, thus making themselves more susceptible to osteoporosis. Others take drugs that block testosterone but can have long-term side effects such as liver toxicity. The remainder just quit athletics altogether.

In the absence of a clear biological line between males and females, Karkazis argues that the fairest solution is to return to the policy of yesteryear, and allow athletes who classify themselves as women to compete as women.