Improvement of infiltrative ophthalmopathy in parallel with decrease of thyroid-stimulating antibody (TSAb) activity in two patients with hypothyroid Graves’ disease

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Abstract
Two patients with primary hypothyroidism associated with infiltrative ophthalmopathy without previous history of hyperthyroidism are presented. Anti-TSH receptor antibodies (TRAb) were detected by radioreceptor assay (TBII), and unexpectedly their biological activity was not of a blocking (TSBAb), but of a thyroid-stimulating type(TSAb). After the initiation of levothyroxine therapy, the TBII and TSAb activities both decreased gradually with normalization of the elevated TSH level. The inflammatory eye signs improved strikingly in parallel with decrease of these antibody activities. These data indicate that (1) TRAb in primary hypothyroidism do not always show TSBAb activity, (2) the decrease in TRAb following levothyroxine therapy in these patients appeared to correlate with suppression of TSH, (3) changes in infiltrative ophthalmopathy were associated with that of TSAb even in primary hypothyroidism, and (4) the hypothyroidism in these patients is justifiably diagnosed as “hypothyroid Graves’ disease”. TSAb might be somewhat related to the pathogenesis of ophthalmopathy in autoimmune thyroid diseases.