TSH receptor antibodies in autoimmune thyroiditis.

Out of 2,322 patients attending a thyroid clinic in north west Germany over a three year period, 123 were found to have evidence of autoimmune thyroiditis (hypothyroid, latent hypothyroid or euthyroid) and 96 were available for further analysis. TSH receptor antibodies (TRAb) were detectable by receptor assay in five of these patients (and a further two who attended the clinic later) and all the TRAb positive sera showed TSH blocking activity by bioassay. All of the patients with blocking activity were hypothyroid (on treatment) and represented 15% of this group of 34 patients. This suggests that in hypothyroid patients with autoimmune thyroiditis, the prevalence of TSH receptor antibodies with blocking activity is similar in northern Europe and Japan (21% of 43 patients; (1]. In the present study, no relationship between thyroid volume as assessed by sonography and the presence or absence of blocking antibodies was apparent. As blocking antibodies were undetectable in patients at early stages of the disease (i.e., in the euthyroid or latent hypothyroid groups) it seemed unlikely that these antibodies were a major causative factor in the development of hypothyroidism.