Testosterone rule for female athletes is unscientific, Canadian researcher says

South Africa's runner Caster Semenya, current 800-meter Olympic gold medalist and world champion, arrives for the first day of her hearing at the international Court of Arbitration for Sport, CAS, in Lausanne, Switzerland, Monday, Feb. 18, 2019. (Laurent Gillieron/Keystone via AP)

MONTREAL -- Proposed rules to limit natural testosterone levels in some female track and field athletes are unscientific and would set a precedent for discriminating against people based on their natural abilities, a Canadian researcher says.

In an editorial published Wednesday in the medical journal BMJ, Universite de Montreal professor Cara Tannenbaum and Sheree Bekker of the University of Bath take aim at restrictions proposed by the international governing body for the sport of athletics. The rules would force female runners with differences of sex development to medically lower their testosterone levels before they could race internationally at distances from 400 meters through the mile.

In an interview, Tannenbaum said there isn't enough evidence to prove that increased testosterone causes improved results, and there's no reason to force women with naturally high hormone levels to compete with men.

"What they're doing is they're essentially defining a female athlete by the (level) of testosterone in her blood, and certainly in medical science we don't define individuals as men and women based on a blood test," Tannenbaum said in a phone interview.

The proposed rules by the International Association of Athletics Federations, or IAAF, would require competitors to maintain testosterone levels to below 5 nanomoles per litre of blood in order to compete in certain events.

However, the governing body agreed last year to delay the implementation of the new rules pending a decision on an appeal brought by two-time 800-metre Olympic champion Caster Semenya, who would be forced to lower her natural hormone levels under the new rules.

The South African athlete appealed the hormone regulations to the Court of Arbitration for Sport, arguing the governing body lacks scientific evidence that testosterone levels substantially enhance sports performance. Semenya's lawyers have said she is facing discrimination for "genetic gifts" that should instead be celebrated.

A panel of judges is expected to announce a decision by March 26.

Tannenbaum, who is scientific director for the Canadian Institutes of Health Research's Institute of Gender and Health, said there is "absolutely zero research" to suggest that high testosterone levels can make someone a great athlete. She said performance depends on multiple factors, including training, skill, and various other physical and mental qualities.

"I bet if you went on the street today and randomly took blood and tested the testosterone of everyone driving from work ... you would probably have people who had the exact testosterone level in their blood as many of the Olympic athletes, but that doesn't mean they could win the Olympics," she said.

The IAAF has disputed the claim that its findings aren't scientific.

"There is a broad medical and scientific consensus, supported by peer-reviewed data and evidence from the field, that the high levels of endogenous testosterone circulating in athletes with certain (differences of sex development) can significantly enhance their sporting performance," the organization wrote last year.

Tannenbaum says the issue raises a host of larger questions, including how to define what separates a male athlete from a female one, and what constitutes an unfair biological advantage, given that most elite athletes have no shortage of genetic gifts that make them faster, taller, or stronger than the vast majority of the population.

"If you're born with bigger feet, should you not be able to play soccer?" she asked. "If you had a genetic superiority because you're very, very tall, should you not be able to play basketball?"

Tannenbaum believes that, at the very least, there needs to be more research before any new rules are adopted to categorize women based on biological measures.

But she also questions why any limits need to be placed on an athlete such as Semenya, who is classified as a woman and identifies as such, just because of her exceptional ability.

"The whole idea of the Olympics is to look for individuals who are born with extraordinary talent or ability," Tannenbaum said.