Effectiveness of newborn screening programs for congenital hypothyroidism: prevalence of missed cases.

The author reviews the background information and technical developments leading to newborn screening for congenital hypothyroidism as well as the effectiveness and problems of the programs during the past decade. The success of the programs in terms of prevention of mental retardation now is clear. It is also clear, however, that a significant number of affected infants, perhaps 8 to 10 per cent of the total, can be missed in the best of screening programs. Physicians must be aware of the possibility and alert to early clinical evidence of congenital hypothyroidism.