The signs and symptoms of hypothyroidism vary widely, depending on the severity of hormone deficiency.

CNN: Hashimoto's disease

Brown said that being treated for hypothyroidism gives his athletes an edge over competitors suffering unknowingly from the affliction.

WSJ: U.S. Track's Unconventional Physician

In a specialty accustomed to treating older women, Brown calls himself a pioneer for finding hypothyroidism in young athletes.

WSJ: U.S. Track's Unconventional Physician

The signs and symptoms are mainly those of an underactive thyroid gland (hypothyroidism).

CNN: Hashimoto's disease

Even within the camp arguing for a broader definition of hypothyroidism, Brown stands apart for diagnosing it in young athletes.

WSJ: U.S. Track's Unconventional Physician

Hendricks had severe congestive heart failure, chronic asthma, uncontrolled diabetes, hypothyroidism, gout, and a history of smoking and alcohol abuse.

NEWYORKER: The Hot Spotters

She was diagnosed with hypothyroidism in 2007.

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It's unclear exactly how many elite athletes are being treated for thyroid disorders, but of the 30 athletes who have trained with Salazar as part of Nike's elite team of distance runners, he said that five or 17% --have been diagnosed with hypothyroidism.

WSJ: U.S. Track's Unconventional Physician