The authors examined in a 82-year-old female patient T4, T3, free T4, TSH, thyroglobulin and made the TRH-TSH functional test because of suspected thyroid disease. For thyroid hormones they obtained controversial resulting levels: in T4 signalizing an unreasonable negative value, in T3 a very high level, in TSH and the TRH-TSH test levels suggesting normal thyroid function which was consistent with the clinical picture. A more detailed laboratory analysis revealed the presence of antibodies binding 125I-T4 and 125I-T3 (radioindicators used for assessment of T4 and T3). The authors identified antibodies against T4, T3 and thyroglobulin. Their presence influenced the radioimmunoassay of T4 and T3 and also the immunoradiometric estimation of thyroglobulin (artificially raised level). The reliable result of the eufunctional condition was not influenced in the estimation of the TSH level.

Keywords: Aged; Aged, 80 and over; Autoantibodies /analysis/; Diagnostic Errors; Female; Humans; Thyroglobulin /immunology/; Thyroid Diseases /diagnosis/; Thyroid Hormones /immunology/; Thyroxine /immunology/; Triiodothyronine /immunology/