Thyrotrophin-binding inhibiting immunoglobulins (TBII) in subacute thyroiditis

The occurrence of thyrotrophin-binding inhibiting immunoglobulins (TBII) was determined by the radioligand receptor method in 8 patients with subacute thyroiditis (ST). In the acute phase 2 out of the 6 cases investigated at this stage were TBII positive and one had a borderline TBII value. All three cases were TBII negative when re-investigated more than 3 months later. In the acute phase the serum thyroglobulin (TG) level was 63.8 +/- 61.9 micrograms/l (mean +/- SD, ref. limit less than 26 micrograms/l) and in the later phase 18.2 +/- 9.3 micrograms/l, the TG level being somewhat higher in the TBII positive cases than in the TBII negative cases. Addition of TG to the TBII assay did not affect the displacement of the labelled TSH from the receptor membranes. The occurrence of TBII may be a secondary phenomenon to the follicular destruction seen in the acute phase of ST and indicated by a rise of serum TG. Nevertheless, TBII in ST has the characteristics of a TSH-receptor antibody and it may interfere with the TSH receptor.