Congenital Goiter in Four Euthyroid Siblings with Glandular and Circulating Iodoproteins and Defective Iodothyronine Synthesis

ABSTRACT Four siblings are reported with a syndrome characterized by a large goiter, circulating iodoprotein, elevated radioiodine thyroid uptake, and negative thiocyanate discharge test. Peripheral deiodination as assessed in 3 patients was normal. Although all 4 patients appeared clinically euthyroid, the low total and free serum T4 and elevated tsh were compatible with hypothyroidism. Total T3 levels were however found to be normal or high, with normal free T3. These discrepancies could not be ascribed to significant abnormalities in thyroid hormone binding proteins. In the 2 glands studied after radioiodine administration, salting out with phosphate buffer suggested the presence of a labeled protein with solubility greater than thyroglobulin. The gel filtration pattern indicated the presence of thyroglobulin and a large amount of iodoalbumin. Chromatography of thyroid hydrolysates showed large quantities of iodotyrosines with a normal MIT/DIT ratio and the virtual absence of labeled iodothyronines, ex...