Alteration in gut microbiota is associated with immune imbalance in Graves’ disease Original paper

What was studied?

This original research study investigated the composition of the gut microbiota in patients with Graves’ disease (GD), an autoimmune thyroid disorder characterized by hyperthyroidism. The focus keyphrase “gut microbiota in Graves’ disease” defines the core of this work, and the study aimed to determine whether there are distinct microbial signatures associated with GD compared to healthy controls. Researchers collected fecal samples from both groups and performed 16S rRNA gene sequencing to analyze the microbial communities present. The study also examined correlations between specific microbial taxa and clinical parameters relevant to GD, such as thyroid hormone levels and autoantibody status, seeking to identify potential microbial biomarkers that could distinguish GD patients from healthy individuals.

Who was studied?

The study population comprised 55 patients with previously diagnosed Graves’ disease and 48 age-, sex-, and BMI-matched healthy controls recruited from a health screening center. All GD patients were under routine follow-up and had been treated with standard anti-thyroid drugs. Controls were screened to exclude thyroid disease and matched for relevant demographic and anthropometric factors. Exclusion criteria for both groups included recent antibiotic or probiotic use, presence of other autoimmune diseases, gastrointestinal disorders, recent gastrointestinal surgery, pregnancy, and strict vegetarianism. This careful selection ensured that observed differences in gut microbiota could be attributed primarily to GD status rather than other confounding factors.

Most important findings

The study found that while overall microbial richness and diversity were similar between GD patients and healthy controls, the global composition of the gut microbiota was significantly different, as demonstrated by principal coordinate analysis and partial least squares-discriminant analysis (ANOSIM p <0.001). Notably, GD patients exhibited a decreased abundance of Firmicutes and an increased abundance of Bacteroidetes and Actinobacteria at the phylum level. At more refined taxonomic levels, GD patients had higher levels of Prevotellaceae, Veillonellaceae, Prevotella_9, Parabacteroides, Collinsella, and Actinomyces_odontolyticus, while healthy controls had higher levels of Lachnospiraceae, Ruminococcaceae, Faecalibacterium, and Lachnospira. Several of these taxa, particularly those enriched in GD, showed strong positive correlations with GD clinical parameters, including TPO antibodies and free T4, and negative correlations with TSH. A random forest classifier using the top 15 most discriminative taxa achieved an AUC of 0.825 for distinguishing GD patients from controls, highlighting the discriminative potential of these gut microbiome signatures.

Key implications

This study provides compelling evidence that the gut microbiota in Graves’ disease is characterized by distinct compositional alterations, despite similar overall diversity compared to healthy individuals. The identification of specific microbial taxa—particularly increased Prevotellaceae, Veillonellaceae, and Prevotella_9, alongside decreased Lachnospiraceae and Faecalibacterium—suggests possible microbial signatures relevant to GD pathogenesis or progression. These findings support the hypothesis that the gut microbiota may influence or reflect immune dysregulation in GD. Clinically, these microbial signatures could potentially serve as non-invasive biomarkers for GD diagnosis or monitoring, and may, in the future, guide the development of microbiota-targeted interventions. Further longitudinal and mechanistic studies are required to elucidate causality and functional consequences.