HOUSTON—On the wall of the medical office of Jeffrey S. Brown is a photograph of Carl Lewis, the nine-time Olympic gold medalist. Lewis is one of several former or current patients of Brown's who have climbed the Olympic podium, including Galen Rupp, who won a silver medal in the 10,000 meters at the London Olympics.

"The patients I've treated have won 15 Olympic gold medals," said Brown.

Among endocrinologists, Brown stands almost alone in believing that endurance athletics can induce early onset of a hormonal imbalance called hypothyroidism, the condition with which he diagnosed Lewis and Rupp. Brown said he knows of no other endocrinologists treating athletes for hypothyroidism, a fatigue-causing condition that typically strikes women middle-aged or older.

Several endocrinology leaders had never heard of hypothyroidism striking young athletes.

"To see large numbers of young, athletic males being treated for thyroid deficiency would be certainly considered unusual, if not a bit suspicious," said Ian Hay, a Mayo Clinic endocrinologist who has practiced for 40 years. P. Reed Larsen, a Harvard Medical School endocrinologist, said, "I can't remember hearing or reading on [thyroid disorders in athletics] and I tend to be more of an investigator-type physician."