[Incidence and functional role of antithyroid antibodies in hyperthyroidism]

INTRODUCTION: We report our personal experience in patients with biochemical hyperthyroidism and no nodules, studying the correlations between antithyroid autoantibodies titers, thyroid function and clinical symptoms. MATERIAL AND METHODS: We examined 93 patients (13 men and 80 women, mean age: 44.6 years, range: 25-68 years) referred for suspected hyperthyroidism. Thyroid 99mTc scintigraphy was performed and the 20 minutes' uptake index (UI) calculated: all these patients had a scintigraphic pattern of normal or enlarged thyroid with homogeneous radiotracer uptake. The presence and titer of antiperoxidase (TPO) and anti-TSH receptor antibodies (TRAB), FT3, FT4, TSH were assayed. Based on the results, the patients were divided into 4 subgroups: A (high TRAB/high TPO, no. 17), B (low TRAB/high TPO, no. 15), C (high TRAB/low TPO, no. 35), D (low TRAB/low TPO, no. 26). The incidence of hyperthyroidism symptoms was 94% in Group A, 40% in Group B, 89% in Group C, 50% in group D. RESULTS: UI significantly correlated with FT3 (p < .001), FT4 (p < .01) and TRAB (p < .01) titers. FT3 and UI average values were significantly higher in Group A and Group C patients (high TRAB) than in Group B and Group D patients (low TRAB) (p < .01); these parameters were significantly higher also in Group A than in Group B patients (p < .05 for FT3 and p < .03 for UI, respectively). Mean intergroup TSH values did not differ (p = ns) and anti-TPO antibodies did not correlate with FT3, FT4 and TSH titers. CONCLUSIONS: UI behaved as a good marker of hyperthyroidism in all patients and TRAB correlated well with organ function and the clinical picture; however, about 18% of patients exhibited no antibody production. No correlation was found between TPO and thyroid function. The lack of antithyroid antibodies seems to indicate a better clinical course for hyperthyroidism. The patients without TRAB and/or with high anti-TPO titers may follow different clinical courses and need a regular follow-up.