Prevalence of thyroid hormone autoantibodies in healthy subjects

Summary OBJECTIVE The prevalence of thyroid hormone autoantibodies in patients with thyroid disorders has been well described, although the results have been variable. However, the prevalence of thyroid hormone autoantibodies in apparently healthy subjects remains unknown and its determination was the main objective of this study. SUBJECTS AND METHODS Sera obtained from 880 healthy subjects (365 men and 515 women) were examined for thyroid hormone autoantibodies by immune precipitation using radiolabelled thyroid hormones or thyroid hormone analogues. RESULTS Anti-triiodothyronine (T3) and anti-thyroxine (T4) antibodies were detected in none (0%) and in 3 (0·34%), respectively, of the 880 individuals studied using radiolabelied thyroid hormones. Similar tests in 385 healthy subjects using radiolabelled thyroid hormone analogues (polyaminocarboxy T3 and T4) showed the presence of anti-T3 and anti-T4 antibodies in 3 (0·78%) and in 4 (1·04%), respectively. None of the subjects had both anti-T3 and anti-T4 antibodies. Thus, the prevalence of anti-T3 or anti-T4 antibodies among healthy population was concluded to be as high as 1·8%. Radiolabelled thyroid hormone analogue binding to purified immuno-globulin G (IgG), with or without the addition of an excess of uniabelled thyroid hormones, confirmed specific binding of thyroid hormones to the thyroid hormone autoanti-body-positive IgGs. The presence and class speciflclty of thyroid hormone autoantibodies was confirmed by the Ouchteriony immunodiffusionlautoradiography method, which showed biphenotypic heavy chain (IgG and IgA) and kappa (κ) light chain specificities. Serum concentrations of free thyroid hormones and TSH in thyroid hormone autoantibody-positive sera were within the normal range. CONCLUSIONS These results indicate that the Occurrence of thyroid hormone autoantibodies among the healthy Japanese population is fairly common. However, interference of thyroid hormone autoantibodies in the radio-Immunnoassay of free thyroid hormones is exceptional.