Abstract

The iodinated blood constituents and the butanol-soluble products of thyroglobulin hydrolysis have been studied in a family of goiterous individuals. The iodinated substances in the blood were in part thyroxine and in part other unidentified iodinated substances. In some individuals there was no identifiable thyroxine. The unidentified products were protein-precipitable, butanol-soluble, dialyzable substances that migrated with the albumin fraction of serum in electrophoresis. Similar substances have been characterized as partial hydrolytic products of rat thyroglobulin and of thyroglobulin obtained from the thyroid gland of one of the goiterous subjects.

The physical characteristics of the substances found in the blood and the hydrolytic products of thyroglobulin suggest that they are either iodinated fats or simple peptides. The conclusion is reached that they are simple peptides. Since large amounts of these substances were isolated from the thyroid, and since repeated hydrolysis could not further degrade them, it is suggested that the structure of thyroglobulin is altered in such a way that these hydrolytic fragments resist further hydrolysis. The genetically determined defect is viewed as a defect in thyroglobulin synthesis, resulting in the release of incompletely hydrolyzed fragments of thyroglobulin.

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