Thyroid autoimmunity and thyroid autonomy

While it is well established that autoimmune factors are the cause of goiter and hyperthyroidism in Graves' disease, these factors are not yet considered relevant in the development of thyroid autonomy. While an increased overall frequency of anti-Tg and anti-TPO antibodies has been found in moderate iodine-deficient areas, where thyroid autonomy is more frequently observed, there was evidence indicating that thyroid autoimmune phenomena were the consequence rather than the cause of the goiter. Thyroid Stimulating Antibodies (TSAb) have been reported in sera of patients with nodular autonomous goiter, but their pathogenetic relevance is uncertain, since these findings could not be confirmed by others. In our experience TSAb were detected in few cases with multinodular nontoxic goiter and were always associated with anti-TG and anti TPO antibodies, indicating that these patients have the nodular variant of Graves' disease. Besides TSAb, Thyroid Growth Stimulating Antibodies (TGAb) have been detected by different techniques in several goitrous conditions, including Graves' disease and sporadic or endemic nontoxic goiter. The precise nature of TGAb remains to be clarified, and particularly the relationship between TGAb and TSAb is still a matter of controversy. However, data indicating that TGAb cannot be dissociated from TSAb in Graves' sera suggest that these antibodies can be regarded as a sufficient pathogenetic agent for the development of both goiter and thyroid hyperfunction in Graves' disease. The relevance of TGAb in euthyroid goitrous conditions is uncertain, since conflicting results have been reported.(ABSTRACT TRUNCATED AT 250 WORDS)