Studies on the Metabolism of L-Diiodotyrosine

3. Defective deiodination of I¹³¹-labeled L-diiodotyrosine in patients with simple goiter

Abstract

A study was made of 10 patients with simple goiter and a defect in deiodination of diiodotyrosine.
Six patients apparently had a defect both in thyroidal and in peripheral deiodination. All of them had an abnormally slow rate of deiodination of administered I¹³¹-labeled L-diiodotyrosine (L-DIT I¹³¹). In vitro studies of the thyroid glands from 3 of these 6 revealed defective deiodination. The other 3 were goitrous cousins of one of them, and presumably had a similar defect. The defective deiodination in these 6 patients persisted after thyroid therapy.
The other 4 patients had a defect in peripheral deiodination. All of them had an abnormality of deiodination of administered L-DIT I¹³¹. Thyroid tissues from 3 of these 4 were tested in vitro, and the deiodinating activity was found to be normal. The fourth was a goitrous daughter of one of them. This defect in peripheral deiodination seemed to be somewhat corrected by thyroid therapy.
Observations made on our patients suggest that a defect in deiodination of iodotyrosines in the periphery or throughout the body would supposedly produce simple goiter and that this defect is transmitted by a dominant and autosomal gene.