TSH RECEPTOR ANTIBODY-ASSOCIATED THYROID-DYSFUNCTION FOLLOWING SUBACUTE THYROIDITIS

OBJECTIVE Autoimmunity plays an important role in the development of t hyrotrophin (TSH) receptor antibodies and the pathogenesis of Graves' disease and Hashimoto's thyroiditis. On the other hand, subacute thyro iditis is a self-limited inflammatory disease of presumed viral aetiol ogy, The aim of this study was to examine whether subacute thyroiditis triggers TSH receptor antibody-associated thyroid disorders. PATIENTS We reviewed 1,697 patients with subacute thyroiditis seen between 198 5 and 1995, DESIGN AND MEASUREMENTS We measured antibodies which inhib it the TSH binding to the TSH receptor (TBIAb), thyroid stimulating an tibodies (TSAb) and antibodies that block TSH action (TBAb), Other thy roid autoantibodies were also determined. RESULTS TBIAb became positiv e in 38 patients following subacute thyroiditis, Thyroid function afte r the development of TBIAb appeared to be influenced by the bioactivit y of the antibody. Hyperthyroidism developed in the presence of TSAb, and so did hypothyroidism in the presence of TBAb, although 21 patient s did not have thyroid dysfunction despite high titres of TBIAb, Fifte en out of 17 patients recovered from hyperthyroidism or hypothyroidism after the disappearance of TBIAb sometimes even without medication. T BIAb-positive patients had a high incidence of a family history of thy roid disease and positive anti-thyroid microsomal antibodies. An ophth almopathy similar to Graves' disease was also observed in 3 patients. CONCLUSIONS Subacute thyroiditis may trigger autoreactive B cells to p roduce TSH receptor antibodies, resulting in TSH receptor antibody-ass ociated thyroid dysfunction in some patients.