The trilateral nexus of autoimmune thyroiditis: integrating immunological triggers, endocrine disruption, and gut microbiome alterations for treatment strategies

The pathogenesis of autoimmune thyroiditis (AIT) is intricately linked to immune dysregulation, endocrine imbalance, and gut microbiota dysbiosis. The immune system drives autoimmune attacks against thyroid tissue through Th1/Th2 cell imbalance, Treg dysfunction, and excessive release of proinflammatory cytokines. Thyroid hormone regulation primarily occurs via the hypothalamic-pituitary-thyroid (HPT) axis. Elevated levels of TPOAb and TgAb in AIT patients can lead to hypothyroidism by affecting the HPT feedback loop. Thyroid hormone regulation of immune cell metabolism and differentiation, in turn, affects immune homeostasis, forming a bidirectional regulatory network. Recent studies further reveal that the gut microbiota influences systemic immune tolerance by regulating intestinal barrier integrity and metabolites (e.g. short-chain fatty acids and secondary bile acids). Abnormal abundance of specific genera (e.g. <i>Bacteroides</i> and <i>Prevotella</i>) can promote the production of thyroid autoantibodies (TPOAb/TgAb), and increased intestinal permeability caused by microbiota dysbiosis may facilitate cross-reactivity between microbial antigens and thyroid antigens. Furthermore, the gut microbiota indirectly regulates thyroid function through the HPT axis. This review aims to summarize the current knowledge regarding the specific molecular mechanisms of gut microbiota-immune-endocrine interactions in AIT, offer important references for researching the treatment directions of AIT.