Title: Human Development and the Thyroid Gland:Relation to Endemic Cretinism
Description: Differentiation of cellular structure and function is the basis for the development of complex organisms; its biochemical foundation is one of the central problems of contemporary biology. More than half a century ago, Gudernatsch demonstrated the role of the thyroid in the metamorphosis of the tadpole into a frog, and showed for the first time that a normal metabolite is indispensable for fulfillment of the scenario of vertebrate maturation. Since then an extensive literature has accumulated which considers the role of the thyroid in animal and especially human development. Nowhere is this role more striking than in cretinism, a term applied to idiocy and physical retardation generally assumed to arise from insufficient thyroid hormone in fetal or neonatal life.

A small group of physicians met at the Institute of Human Biology in Goroka, New Guinea, in January 1971 to consider the nature and prevention of those varieties of cretinism which occur in association with endemic goiter and which are grouped under the term endemic cretinism. Curiously, for centuries this disorder has occupied a distinctive niche under the panoply of mental retardation, and yet it has defied the kind of formal definition which would permit unequivocal ascertainment in individual cases. Indeed, the pathogenesis and even its relationship to the thyroid have remained obscure and controversial. The Goroka meeting was successful in resolving some of the conflicting information regarding the various clinical manifestations of cretinism and in underlining the effectiveness of prophylactic use of iodine in preventing its appearance. The need for additional information from a broader spectrum of medical scientists was apparent.

The present monograph, comprising the proceedings of a conference on endemic cretinism and the thyroid in human development, is a direct extension of the Goroka conference. The symposium was sponsored by The Kroc Foundation and took place January 1972 at their headquarters - the J & R Double Arch Ranch of the Founder, Ray A. Kroc, in the Santa Ynez Valley of California. The initial papers were concerned with descriptions of endemic cretinism by investigators who have had direct experience with field studies in various parts of the world. Reports were presented from Andean South America, the Himalayas, New Guinea, Switzerland, Italy, and Central Africa. Resolution of some of the seemingly conflicting information was achieved. The conference then addressed the problems of definition, assessment, and field ascertainment of cretinism.

The difficulties caused by cultural and language barriers in the detection of retardation was explored, and the unusual difficulty posed by deafness, a common but not invariable accompaniment of endemic cretinism, was considered. With the clinical patterns of the disease assembled and the experimental approaches identified, an attempt was made to arrive at a formal definition of endemic cretinism which could be operationally adequate and which would permit better communication among investigators. This was followed by a review of preventive measures. The most important data which have become available in recent years derive from observations made after administration of depot iodized oil. Experience obtained in such programs in New Guinea, Peru, Ecuador and the Zaire Republic were reported. A consensus was reached that the method is feasible, safe, and probably effective, although the small numbers of retardates born in control groups makes this uncertain.

The discussion then turned to the hearing problems in endemic cretinism, with consideration of its embryological, pathological and experimental aspects. This lead naturally into a consideration of the role of thyroid hormone in the development of the central nervous system, and the interactions between the thyroid and environmental factors, such as nutrition, in central nervous system maturation. The final presentations related to the etiopathogenesis of the developmental abnormalities of endemic cretinism. The relative contributions of maternal and fetal thyroids to embryogenesis were assessed, and toxins from the environment which might act specifically on thyroid function, such as cyanogenic glycosides, were identified. The conference closed with a discussion of the pathophysiology of the thyroid in the clinical variants of endemic cretinism.
Subjects: Thyroid Gland, Congresses, Congenital Hypothyroidism, Crétinisme, Thyroïde, Congrès, Cretinism, Congenial hypothyrodism