The global prevalence of neurodevelopmental diseases is on the rise. The number of autistic babies in the US has jumped from 1 in 68 to 1 in 42. Plus more and more children have attention disorders or hyperactivity disorders. The genetic causes of these disorders of neurological development cannot explain such radical increases in the incidence and this leads one to look for the culprit in other elements, many of which have been shown to disrupt normal thyroid function. For instance, many polluting chemical substances can interfere with thyroid hormone (TH) metabolism and this might lead to abnormalities in the neurological development of the fetus or the child.