Thyrotropin binding inhibiting immunoglobulins (TBII) in Graves' disease, toxic nodular goitre and autoimmune thyroiditis

Abstract

The occurrence of thyrotropin binding inhibiting immunoglobulins (TBII) was studied in 144 patients with different types and stages of Graves' disease (GD) including 2 patients with primary hypothyroidism which changed into hyperthyroid GD. TBII were also studied in 17 patients with toxic nodular goitre (TNG) and 29 patients with autoimmune thyroiditis. TBII was determined with a radioligand receptor assay and expressed as a TBII index which was defined as percentage binding of 125-I-labelled bovine TSH to a thyroid membrane fraction in the presence of test immunoglobulins in comparison with the maximal binding. TBII were positive in 69% of patients with untreated hyperthyroid GD, in 65% after 3-6 months of antithyroid treatment, and in 30-40% 3-114 months after discontinuation of therapy. During treatment the TBII index increased slowly towards normal levels differing significantly from the value before therapy not earlier than after at least 12 months' treatment. Both patients with primary hypothyroidism who developed hyperthyroid GD were strongly TBII positive. In patients with TNG TBII were positive in 24%. In about 30% of the patients with Hashimoto's thyroiditis and with spontaneous hypothyroidism positive TBII were registered. Also in 2 out of 9 patients (22%) with symptomless autoimmune thyroiditis TBII were positive. TBII are not specific for hyperthyroid GD but nevertheless useful humoral markers in several types of thyroid disorder.