Leaders at the World Anti-Doping Agency (WADA) say there's no scientific reason to ban thyroid medication, despite reports that some high-profile long-distance runners use the medicine during training.
After reports that a number of athletes coached by former Boston and New York Marathon winner Alberto Salazar use the medication, the British anti-doping agency and others asked WADA to consider putting it on its banned-substance list.
But when the list came out last week, that medicine wasn't on it.
Olivier Rabin, the science director at WADA, said Wednesday that because the medicine stops the body from producing its own hormones once they reach a certain level, there's no scientific reason to believe it enhances performance.
He called athletes using thyroid medicine an example of the "medicalization of sports."
"That's a reality," Rabin said. "But our job is to draw a line between what is doping and what is not doping."
The U.S. Anti-Doping Agency is investigating Salazar, who has been accused of skirting anti-doping rules while training some of his athletes.
Among the allegations leveled against Salazar in a story this summer by ProPublica and the BBC was that he told his athletes to get prescriptions for thyroid medication before they started training with him at the Nike Oregon Project.
Among those using the medicine were Galen Rupp, the 2012 Olympic silver medalist at 10,000 meters. In an open letter defending his program, Salazar said Rupp is one of five athletes — out of 55 he has coached — who have been diagnosed with thyroid disease.
Thyroid medication is sometimes used to control weight or act as a stimulant. Data from the American Thyroid Association website said more than 12 percent of the U.S. population will develop a thyroid condition during their lifetime. It said women are between five and eight times more likely to develop a condition than men.
The WADA banned list is reviewed every year, and it's possible the status of thyroid medication could change.
"I tend to be prudent because science tends to evolve," said WADA chief operating officer Olivier Niggli. "I'm always suspicious when so many of them are using it. So, if they do use it, what benefit do they find? But we have to rely on science. Today, science is telling us, 'No, we don't think it works.' But I think we're going to stay awake on this subject."