THE SYNDROME OF CONGENITAL HYPOTHYROIDISM WITH DEFECTIVE DEHALOGENATION OF IODOTYROSINES. FURTHER OBSERVATIONS AND A DISCUSSION OF THE PATHOPHYSIOLOGY

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Abstract
Observations are presented on 3 patients with congenital hypothyroidism and defective dehalogenation of iodotyrosines. In one, the inability of thyroid tissue to deiodinate diiodotyrosine was demonstrated in vitro. The same patient was found to have an extremely low thyroidal iodine content. A trend of iodine metabolism towards a more normal pattern was observed in one of the patients after a period of treatment with desiccated thyroid, but defective dehalogenation of iodotyrosines persisted. The findings in these 3 patients are contrasted with those in a fourth patient, who appeared to have congenital hypothyroidism caused by a specific defect in thyroxine synthesis. Metabolism of diiodotyrosine by thyroid tissue and after intravenous administration was found to be normal in this patient. The available evidence concerning congenital hypothyroidism with defective dehalogenation, and the significance of the principal abnormalities found in this disorder, are critically analyzed. The conclusion is reached that the defects demonstrated in this type of congenital hypothyroidism are sufficiently distinctive to permit its recognition as a separate entity.