THYROIDAL DEIODINATION DEFECT IN THREE SISTERS WITH SIMPLE GOITER.

Abstract

Three goitrous sisters showed normal PBI and BMR values, but high 131I uptakes. In all of them thyroid tissue was nearly inactive in deiodination of 131I-labeled L-diiodotyrosine in vitro, while the rate of deiodination of 131I-labeled l-diiodotyrosine administered intravenously was normal. This finding shows that the sisters share defective deiodinating activity of the thyroid, but that the peripheral activity remains intact. The deiodinating activity was found to be defective even after thyroid replacement therapy. The enlargement of thyroid in these cases is probably to be ascribed to the lack of deiodinating activity of the organ. The mating that produced these goitrous sisters was between first cousins. So far as could be ascertained, these sisters were the only goitrous members of the family. This suggests that the defect is due to an autosomal recessive gene which has a sex-controlled tendency in manifestation.