editorials April 01, 2015 April 01, 2015

Autoimmune thyroid disease: What secrets we still need to unravel?

DOI: 10.1590/2359-3997000000019

Autoimmune thyroid disease (AITD) has been considered the prototypical and the most prevalent organ-specific autoimmune disorder, affecting 2% to 5% of iodine-sufficient population (). This condition encompasses a clinical-pathological spectrum of different phenotypes varying from hyperthyroidism in Graves’ disease to hypothyroidism in Hashimoto’s thyroiditis, probably representing the net effect of a complex mechanism causing break of tolerance to thyroid proteins through interaction between genetic susceptibility and environmental triggers (-). The rational for this theory is based on both family studies and in twins based studies showing respectively a higher frequency of AITD in the relatives of an affected individual and a higher but not complete concordance among identical twins ().

Several genes have been associated with AITD, including immune-response genes (HLADRA II and CD40), T-cell regulation genes (CTLA4, PTPN22, CD25), and thyroid-specific antigens genes (TG, and TSHR). However, these genes together probably do not confer more than about 10% of the genetic susceptibility for AITD (). In other words, there is no single or dominant gene strong enough to confer major susceptibility to AITD. Thus, the disease seems likely to result from the combined effect of multiple genes (-).

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