American Journal of Clinical Nutrition, Vol 25, 30-40, Copyright © 1972 by The American Society for Clinical Nutrition, Inc.

Further investigations of iodine deficiency in the etiology of endemic goiter

¹ From the medical section of the Centre d'Études Scientifiques et Médicales de l'Université de Bruxelles en Afrique Centrale (CEMUBAC) auprès de l'Institut pour la Recherche Scientifique en Afrique Centrale (IRSAC)

Endemic goiter prevalence has been systematically measured in 85% of the population of Idjwi Island. The average prevalence of goiter on the island as a whole is 32.3%. There are very marked geographical variations. Three regions are distinguishable: a hyperendemic region in the north, where the average prevalence of goiter is 52.8%, a region with very low endemicity (7.7%) in the southwest, and a region of intermediate severity (26.0%) in the southeast. There is a distinct relationship between goiter prevalence and age and sex. The familial tendency to goiter on Idjwi is only slight and may be explained either by a form of multigenic heredity or by the intervention of etiological factors of the microenvironment.

Relationships between regional goiter prevalence and parameters of thyroid function were studied in 693 subjects from 30 villages scattered throughout the island. No relationship was observed between goiter prevalence and the degree of iodine deficiency: this deficiency is homogeneous and severe throughout the island. The rise in the level of goiter prevalence is accompanied by a significant increase of ¹³¹I thyroidal uptake at the 6th hr and by a significant decrease in the PB ¹²⁷I level in the plasma.

In goitrous adults, thyroidal uptake is higher and PBI lower than in nongoitrous adults. However, the modifications of thyroid metabolism are influenced far less by the presence or absence of goiter in a particular subject than by regional variations in the prevalence of goiter.

Iodine deficiency constitutes the main etiological factor of endemic goiter on Idjwi Island. However, the pattern of goiter prevalence and the extent to which thyroid metabolism varies cannot be explained by the degree of iodine deficiency; we show that they are determined essentially by a geographical factor. This factor is closely related to the nature of the soil. Furthermore, when compared with nongoitrous subjects, goitrous individuals appear to be less efficient in their adaptation to environmental conditions in the Idjwi endemic goiter area.

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