Normal Peroxidase Activity in Pendred's Syndrome

Abstract

A 12-year-old euthyroid girl with a goiter and bilateral nerve deafness had a 29% discharge of radioiodide after perchlorate. Both parents and five siblings were euthyroid with goiter and nerve deafness, and all but the father had a positive perchlorate discharge of radioiodide. Thyroid tissue obtained during subtotal thyroidectomy contained ample peroxidase activity as measured by I3– formation and 131I incorporation into tyrosine, both of which were stimulated by the addition of hematin. There was a low iodine content in the gland which probably accounted for an increase in MIT/DIT ratio and decrease in the amount of radioiodine found in the iodothyronines, after it had been labelled in vivo with 125I. The thyroglobulin appeared to be normal by its saltingout behavior, chromatography on Sephadex G-200 and immunodiffusion. The findings suggest that the defect in the iodinating mechanism in Pendred's syndrome is a deficiency other than peroxidase activity.