A Retrospective View of Iodine Deficiency, Brain Development, and Behavior From Studies in Ecuador

B eginning in the early 1960s Rodrigo FierroBenitez and his colleagues (1) carried out an extensive series of studies of endemic goiter and cretinism in Ecuador. This chapter will review the most salient aspects of these findings. The investigations by Fierro-Benitez and his group were carried out mainly in eight rural villages in the north and central highlands of Ecuador where surveys indicated that the prevalence of goiter ranged from 3 to close to 55% of the total popu­ lation. Because iodized salt was not widely avail­ able in Ecuador at that time, it was decided to evaluate the efficacy and safety of depot iodination as a means of ameliorating the problem of iodine malnutrition and its subsequent develop­ mental sequelae. To that end a program of de­ pot iodination was begun in one village (Tocachi) and the population of a second nearby village served as a noniodinated control (2,3)The pop­ ulations of these villages and the children born into them have subsequently been studied lon­ gitudinally and constitute a unique corpus of data on the epidemiology of endemic goiter and cretinism and associated developmental defects in highland Ecuador and the effect of this pub­ lic health intervention on the children born into these isolated rural communities. Tocachi (the iodinated community) and La Esperanza (the noniodinated community) are lo­ cated in the Province of Pichincha approximately 70 k north of Quito. The communities are lo­ cated 6 miles apart, with Tocachi at an altitude of 2952 m and La Esperanza at an altitude of 2993 m. The communities are generally compa­ rable, although significant differences do exist which will be discussed below. In March 1966 the population of Tocachi was 1100 and that of La Esperanza was 2500. Just prior to the begin­ ning of the iodination program the prevalence of goiter was 69.7% in Tocachi and 52.8% in La Esperanza and the prevalence of cretinism was 8.2% in Tocachi and 6.0% in La Esperanza. Uri­ nary iodine excretion was 10.4 ng/0.9 g creati­ nine in Tocachi and 17.7 in La Esperanza (2). In March 1966 a public health program of depot iodination was begun in Tocachi with La Esper­ anza serving as the noniodinated control popu­ lation. The following discussion of these studies is divided into four parts that review different as­ pects of the neural consequences of iodine mal­ nutrition. The first section presents an overview of endemic cretinism in these communities that serves to provide a baseline description of the severe neurological deficits observed in these populations. The second section discusses the program of depot iodination and its effect in eliminating endemic cretinism. It also reviews, in some detail, the studies that have evaluated the impact of the iodination program in amelio­