HLA-DRB1 and autoimmune gastritis: Specific HLA alleles, including HLA-DRB1*03 and HLA-DRB1*04, have also been implicated in the co-occurrence of AITD with autoimmune gastritis (Zantut-Wittmann et al., 2004[118], Sartoris et al., 2024[89]), suggesting a common immunogenetic susceptibility in thyrogastric syndrome.