It essentially disappeared after some food makers started adding it to table salt, bread and some other foods, in one of the great public health success stories of the 20th century.

Although most people are still getting enough, researchers have increasingly been reporting low levels of iodine in pregnant women and other people, raising concerns about an impact on their newborns. And there is also a very small, but growing, number of reports of iodine deficiency in kids.

Doctors were puzzled. Testing ruled out their first suspicion. But further tests pinpointed what they -- and the boy -- had been missing: iodine. A century ago, iodine deficiency affected kids across large swaths of the country.