[Incidence and functional role of antithyroid antibodies in hyperthyroidism]

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.

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.

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.

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.