Clinical value of a bispecific antibody binding to thyroglobulin and thyroperoxidase (TGPO-aAb) in various thyroid diseases

TGPO-aAb is a bispecific antibody which binds to thyroglobulin as a ell as thyroid peroxidase. It is supposed to be raised in some patients with autoi mmune thyroid disease. We investigated 205 patients suffering from craves' disease (n = 81), Hashimoto's thyroiditis (n = 36), toxic nodular goitre (n = 50), differentiated carcinoma of the thyroid (n = 10), and autoimmune th yropathy of unknown origin (n = 28). An immunoradiometric assay was used to measure serum TGPO-aAb. Eighty-nine of 205 patients had elevated titres of TGPO-aAb. If TGPO-aAb were raised then autoantibodies against thyroglobuli n and thyroid peroxidase were always raised, too. This was, however, not tr ue vice versa. We found TCPO-aAb in 61% of patients with Hashimoto's, 49% o f patients with Graves', 64% of patients with autoimmune thyropathy, but on ly in 12% of patients with toxic nodular goitre. In patients with thyroid c arcinoma TGPO-aAb was found only if there was evidence of paraneoplastic au toimmune thyroiditis. We re-examined 16 of 36 patients with Hashimoto's thy roiditis after 1 year: 8 patients had retained their raised TGPO-aAb, 1 pat ients showed no TGPO-aAb on both occasions, and 4 patients had 'lost' their previously raised TGPO-aAb on follow-up. We conclude that TGPO-aAb may pro vide additional information in Hashimoto's thyroiditis. Determination of TG PO-aAb does not allow to distinguish between various forms of autoimmune th yroid disease. Nevertheless, the presence of TGPO-aAb and its variation dur ing the natural course of autoimmune thyroid disease remains to be understo od which would give a better insight into its clinical significance.