autoantibodies against thyroid hormones (THAb) are the rarest thyroid antibodies . The overall prevalence of THAb among European consecutive patients attending thyroid clinics is 149 in 369,000 or 0.04% . Their rate of detection does not increase if they are searched in the isolated Ig fraction of serum rather than in serum , confirming that their rarity is real.

According to a European survey , THAb against T₃, against T₄, and against both accounted for 51%, 28%, and 21% of the cases, respectively. THAb coexisted with antibodies to thyroglobulin (TgAb) or Ab to microsomes, now called thyroid peroxidase (TPOAb), in 46% and 6% of patients, respectively . THAb have been reported to be of the IgG class virtually always, because this is the class typically sought