Environmental exposures and infections are hypothesised to induce thyroid autoimmunity by ‘molecular mimicry’ (cross-reactivity between microbial antigens or exogenous agents and the TSHR) or ‘bystander activation’ (non-antigen-specific activation of autoreactive lymphocytes), turning a defensive immune response into autoimmunity.9 Environmental factors have also been proposed to trigger thyroid autoimmunity through epigenetic dysregulation modulating gene expression in susceptible individuals.10 This evidence concerns the gene TSHR and Autoimmunity.