Thyrotrophin Displacement Activity of Serum Immunoglobulins in Health and Disease

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Abstract
A radioreceptor assay for TSH [thyrotropin] displacement activity (TDA) was employed as an index of thyroid stimulating immunoglobulins (TSIg) in serum from patients with autoimmune thyroid disease. TDA was .ltoreq. 20 in normal subjects (37/37), patients without thyroid disease (36/38), non-toxic goiter (18/19) and toxic nodular goiter (16/17) and was significantly lower in Nepalese subjects with severe endemic goiter. TDA was > 20 in 84% of patients with untreated hyperthyroid Graves'' disease (70/83), in Hashimoto''s thyroiditis (3/17) and following subtotal thyroidectomy (8/14) or 131I therapy (7/11), but was .ltoreq. 20 in euthyroid patients treated with carbimazole (58/59) and during spontaneous remission (18/19). Serial TDA measurements during anti-thyroid drug therapy suggested that carbimazole has a direct effect in reducing TSIg concentration but that TDA is not a useful prognostic indicator of short term relapse or remission.