Microbiome Mediated Immune Crosstalk on the Gut-Thyroid Axis in Autoimmune Thyroid Disease

The gut microbiota plays an important role in systemic immune homeostasis and is increasingly implicated in autoimmune thyroid disease (AITD). Evidence suggests that gut dysbiosis, impaired intestinal barrier function, and altered microbial metabolites particularly short-chain fatty acids contribute to immune imbalance along the gut-thyroid axis. Although molecular mimicry between microbial and thyroid antigens has been proposed, current human evidence remains associative rather than causal.

This review synthesized current observational, translational, and preclinical studies evaluating microbial composition, barrier integrity, microbial metabolites, and immune pathways relevant to AITD. Mechanistic insights into T-lymphocyte regulation and microbial-host interactions were integrated with emerging interventional data.

Gut dysbiosis in AITD is linked to reduced regulatory T-lymphocytes, expansion of Th17 cells, increased intestinal permeability, and the loss of short-chain-fatty-acid-producing taxa. Observational studies consistently report disease-associated taxonomic alterations, while preclinical models support causal pathways through barrier disruption and microbiota-driven immune activation. Early interventional approaches such as high-fiber dietary patterns, probiotics, prebiotics, and experimental fecal microbiota transplantation show modest reductions in thyroid autoantibodies in small trials, though effects are strain-specific, short-term, and not disease-modifying.

Despite largely associative human evidence, converging mechanistic findings highlight the gut microbiota as a modifiable contributor to thyroid autoimmunity. Future priorities include clarifying causality, identifying keystone microbial taxa and metabolites, and establishing standardized interventional frameworks to facilitate translation into endocrine practice.