Systematic screening for congenital hypothyroidism in the newborn was introduced some 15 years ago. The main objective was the prevention of mental retardation due to thyroid hormone deficiency during the early months of life. During the past decade screening programs have become routine throughout most of the industrialized world and many questions relating to implementation, organization and quality control of such programs have been largely resolved. Preliminary IQ and neurological data have indicated that screening and early treatment do, in fact, prevent mental retardation. However, a...