Gut Microbiota and Thyroid Diseases: A Comprehensive Review of Mechanisms and Clinical Implications

Abstract

The interplay between gut microbiota and thyroid diseases has emerged as a cutting-edge topic in endocrinology and microbiome research. Accumulating evidence indicates that gut microbes not only influence thyroid hormone synthesis and metabolism through metabolites such as short-chain fatty acids and bile acids, but also play critical roles in immune homeostasis, thereby contributing to the pathogenesis and progression of Graves' disease, Hashimoto's thyroiditis, thyroid dysfunction, and thyroid cancer. Epidemiological and clinical studies suggest that specific microbial signatures are associated with disease risk, subtype classification, therapeutic response, and recurrence, highlighting their potential as diagnostic and prognostic biomarkers. Emerging interventions, including probiotics, dietary modulation, and fecal microbiota transplantation, have shown promising effects in animal models and preliminary clinical studies, offering new opportunities for personalized management. Nevertheless, current research faces notable challenges: causal relationships remain unclear, disease heterogeneity and population differences compromise reproducibility, and biases inherent to low-biomass samples and sequencing methodologies limit evidence strength. Future investigations should focus on standardized protocols, cross-cohort validation, multi-omics integration, and mechanistic trials to elucidate the biological basis of the “gut–thyroid axis” and accelerate its translation into clinical diagnostics, risk stratification, and therapeutic interventions.