Thyroid Blocking Antibodies in Thyroiditis

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Abstract
Serum from a woman with a history of Hashimoto''s thyroiditis, who had given birth to 2 children with congenital hypothyroidism, contained potent TSH blocking activity. Immunoglobulin preparation from this serum abolished completely TSH-stimulated cAMP production in human thyroid membranes. The blocking activity was associated with the IgG fraction absorbed to and eluted from a Protein A column. The stimulation of adenylate cyclase by a preparation of thyroid-stimulating antibodies from a patient with Graves'' disease was also inhibited by the antibodies. No effect was observed upon fluoride-stimulated cAMP production. The antibody activity was apparently directed against the TSH receptor. Immunoglobulin preparations from 22 other patients with Hashimoto''s thyroiditis and 16 patients with subacute thyroiditis were examined for the existence of TSH receptor blocking antibodies. A blocking activity was found in 2 of the 22 Hashimoto patients. No such activity was found in the patients with subacute thyroiditis. Thyroid blocking antibodies sometimes contribute to hypothyroidism associated with Hashimoto''s thyroiditis.