ANTI-THYROXINE AND ANTI-TRIIODOTHYRONINE ANTIBODIES IN THREE CASES OF HASHIMOTO'S THYROIDITIS

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Abstract
Antibodies [Ab] against thyroxine (T4) and/or triiodothyronine (T3) were detected in 3 patients with Hashimoto''s thyroiditis. One of the patients had both anti-T4 and anti-T3 Ab and the other 2 patients had only anti-T3 Ab. Serum T4 or T3 values measured by the single Ab radioimmunoassay (RIA), were low or nil in these patients. One patient was mildly hypothyroid. The other 2 patients were clinically euthyroid, but they were considered latent hypothyroid because of a slight elevation in serum TSH [thyrotropin]. On extraction of the sera with ethanol, high or normal values of T3 were obtained in all cases. Recovery of T4 or T3 added to the patients'' sera determined by RIA was significantly low. The binding of [125I]T4 or [125I]T3 to the patients'' sera was demonstrated by the polyethylene glycol method and by using RIA kits without adding the Ab provided. The binding activity was localized in the Ig[immunoglobulin]G fraction by column chromatography and by immunoprecipitation. T4- or T3-binding protein in 2 sera migrated in the .gamma.-globulin region on paper electrophoresis and was found in the 7S fraction on Sephadex G-200 chromatography. In 1 serum containing both anti-T4 and anti-T3 Ab, the association constants (Ka) for binding of T4 and T3 were 3.8 .times. 108 l/mol and 1.7 .times. 108 l/mol. respectively. The binding capacities in the serum were 8.2 .mu.g of T4 and 1.9 .mu.g of T3 per 100 ml of serum. For 2 sera containing anti-T3 Ab, Ka were 5.5 .times. 108 l/mol and 7.4 .times. 1010 l/mol, and the binding capacities were 0.6 .mu.g/100 ml serum and 0.7 .mu.g/100 ml serum, respectively. The clinical significance of these Ab was discussed.

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