Chronic Thyroiditis and Autoimmunization

• An explanation of chronic thyroiditis in man was sought in observations made on rabbits, dogs, guinea pigs, and human subjects. The rabbits received injections of saline extracts of rabbit thyroid glands. The tests for circulating autoantibodies utilized the phenomena of precipitation, complement fixation, and tanned-cell hemagglutination. The third of these, based upon the principle of altering the surface of the red blood cells by dilute tannic acid so that they absorb proteins, was particularly sensitive. The three tests were applied to serums from 35 rabbits injected with rabbit thyroid extract, and thyroid autoantibodies were found in 32. Structural damage was found in the thyroid roughly in proportion to the autoantibody titer in the serum. Similar studies were carried out in dogs and guinea pigs with canine and guinea pig thyroid extracts respectively. The three tests were then applied to serums from patients with chronic thyroiditis. Twelve such patients were found whose serums contained circulating antibodies specifically directed against extracts of human thyroid glands. Three typical case histories are given, with histological findings on thyroid tissue removed during surgery. Six other patients with chronic thyroiditis, proved histologically, were not found to have autoantibodies in their serums at the time of study. These findings lead to the hypotheses that some types of chronic thyroiditis are related to an autoimmunization process within the patient against his own thyroid tissue, and that thyroid autoantibodies are at once indicators and links in the chain of pathological processes.