Thyroid Antibodies After131I Treatment for Hyperthyroidism

Abstract

Antibodies to thyroglobulin and cytoplasmic antigen have been studied by immunofluorescence, tanned cell hemagglutination and complement fixation methods in 115 patients before I131 treatment for hyperthyroidism, in 439 patients after such therapy, and in 29 patients after surgical treatment for hyperthyroidism. During the 1st year after the radioiodine therapy there was a significant increase in the cytoplasmic antibodies; no such rise was observed for the thyroglobulin antibodies. Subsequently, the thyroid antibody titers fell steadily below the pretreatment level. Surgical treatment for hyperthyroidism was found to result in a significant decrease in humoral thyroid antibodies within one year. At the examination carried out during the year after the radioiodine therapy, thyroid antibodies were found in a greater proportion of patients who developed hypothyroidism than in others. At a later examination no such difference was found. Thyroid antibodies were found in a greater proportion of patients cured by one radioiodine treatment than in those requiring several treatments, and more often in younger than older patients of the age group studied. Radioiodine treatment of a hyperactive thyroid gland results in an auto-immune reaction, which is reflected in an increase in the humoral antibodies. The serological pattern, however, showed no resemblance to that in chronic auto-immune thyroiditis. The increase in humoral antibodies is transient, and confined to cytoplasmic antibodies, and the titers are much lower than those observed in chronic auto-immune thyroiditis. There was no evidence that I131 therapy initiates a progressive auto-immune process.