The high prevalence of anti-Neu5Gc antibodies in patients with hypothyroidism (42.1%, P < 0.000) and in patients with Hashimoto disease (97.1%, P < 0.000) compared to the general population (6.0%) and the increased incidence of anti-TPO antibodies in patients with high anti-Neu5Gc concentration raise the concept of a probable association between anti-Neu5Gc antibody development and autoimmune hypothyroidism. Here, TPO is linked to Hashimoto thyroiditis.