ZUR HISTOTOPOGRAPHIE DES JODSTOFFWECHSELS IN ENDEMISCHEN STRUMEN UND IN GESUNDEN SCHILDDRÜSEN

Abstract

ABSTRACT 55 patients from endemic goiter areas in western Austria were studied. 47 of them were goitrous, 8 had normal thyroids and served as controls. After the thyroidal iodine kinetics were followed with 125I, thyroid tissue was obtained by excision and examined with chemical methods and autoradiography. The results give further evidence for the existence of 2 thyroidal iodine pools in goiters, while no similar conclusion could be made in the controls. The distribution of radioactivity in goiters was very unhomogenous. Our findings allowed a classification of euthyroid goiters in cases with low thyroidal iodine concentration (44 ± 11.7 μgI/g) and in iodine rich glands (156 ± 40.0 μgI/g). Both groups showed a rapid iodine turnover, normal uptake and a microfollicular structure on sections. In goiters with a high iodine concentration only a few follicles were active, the MIT/DIT-ratio was below 1. Low iodine goiters had more labelled follicles, a high MIT/DIT-ratio and there was an unexpected positive correlation between daily urinary I-excretion and radio-iodine – uptake values, which is explained by the assumption that the iodine metabolism of these patients was not in equilibrium. The lack of epithelial activity in major parts of goitrous thyroids is understood as a severe disturbance in the adaptation to a proven iodine deficiency and is partly made responsible for the development of a moderate thyroid enlargement in endemic goiter zones into large goiters with tracheal and vascular obstruction. This partial inactivity of goitrous parenchyma is suggestive of regressive changes on the molecular level in endemic goiters.