The disorders induced by iodine deficiency affect at least one billion people. Because ofits effects on brain development, iodinedeficiency is the single most preventable cause of mental retardation in the world. Therefore, the United Nations and the Heads of State of almost all the world's countries represented at the Summit for Children in 1990 adopted resolutions to eradicate the disorders induced by iodine deficiency (IDD) by the year 2000. For geological and socio-economic reasons, most of the populations affected by iodine deficiency disorders live in isolated and usually mountainous areas, in pre industrialized parts ofthe world. The problem of iodine deficiency in Europe has been greatly underestimated in the last decades. After the remarkable studies on the effects of iodine deficiency and their prevention and correction in Switzerland, IDD was generally considered no longer a significant public health problem in Europe. However, surveys carried out in the early 1980's under the auspices of the European Thyroid Association, clearly demonstrated the persistence of moderately or even severely affected areas. These surveys also highlighted the lack ofinformation about large parts ofEurope, especially its eastern part. It is only quite recently, following major changes in international relations and thanks to the support of UNICEF, WHO, the International Council for the Control of Iodine Deficiency Disorders and the European Thyroid Association, that more extensive surveys have been conducted in several parts of Europe hitherto almost unexplored. These surveys showed that most European countries were iodine deficient."

The disorders induced by iodine deficiency affect at least one billion people. Because ofits effects on brain development, iodinedeficiency is the single most preventable cause of mental retardation in the world. Therefore, the United Nations and the Heads of State of almost all the world's countries represented at the Summit for Children in 1990 adopted resolutions to eradicate the disorders induced by iodine deficiency (IDD) by the year 2000. For geological and socio-economic reasons, most of the populations affected by iodine deficiency disorders live in isolated and usually mountainous areas, in pre industrialized parts ofthe world. The problem of iodine deficiency in Europe has been greatly underestimated in the last decades. After the remarkable studies on the effects of iodine deficiency and their prevention and correction in Switzerland, IDD was generally considered no longer a significant public health problem in Europe. However, surveys carried out in the early 1980's under the auspices of the European Thyroid Association, clearly demonstrated the persistence of moderately or even severely affected areas. These surveys also highlighted the lack ofinformation about large parts ofEurope, especially its eastern part. It is only quite recently, following major changes in international relations and thanks to the support of UNICEF, WHO, the International Council for the Control of Iodine Deficiency Disorders and the European Thyroid Association, that more extensive surveys have been conducted in several parts of Europe hitherto almost unexplored. These surveys showed that most European countries were iodine deficient."

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 number of scientific questions related to congenital hypothyroidism remain unanswered and extensive research activities are ongoing in the field. The objective of the organizers of the Brussels workshop was to focus almost exclusively on these current research aspects of the screening programs. This workshop is the third international conference specifically devoted to neonatal thyroid screening. The first was held in La Malbaie in Quebec in the fall of 1979. That meeting was well organized and highly productive. Its proceedings constitute a bible in the field. After the Quebec meeting, we witnessed major and rapid advances in our understanding of neonatal thyroid physiology as well as screening methodology, organiza tion, data management, the significance of an approach to false negative and false positive results,patient follow-up, and assessment of follow-up and treatment, and the psychoneurological evaluation of affected infants. Some of these aspects were further developed during a second highly pro ductive international conference organized in Tokyo in 1982.