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Context: Gut bacteria can influence host immune responses but little is known about their role in tolerance-loss mechanisms in Graves disease (GD; hyperthyroidism caused by autoantibodies, TRAb, to the thyrotropin receptor, TSHR) and its progression to Graves orbitopathy (GO)., Objective: This work aimed to compare the fecal microbiota in GD patients, with GO of varying severity, and healthy controls (HCs)., Methods: Patients were recruited from 4 European countries (105 GD patients, 41 HCs) for an observational study with cross-sectional and longitudinal components., Results: At recruitment, when patients were hyperthyroid and TRAb positive, Actinobacteria were significantly increased and Bacteroidetes significantly decreased in GD/GO compared with HCs. The Firmicutes to Bacteroidetes (F:B) ratio was significantly higher in GD/GO than in HCs. Differential abundance of 15 genera was observed in patients, being most skewed in mild GO. Bacteroides displayed positive and negative correlations with TSH and free thyroxine, respectively, and was also significantly associated with smoking in GO; smoking is a risk factor for GO but not GD. Longitudinal analyses revealed that the presence of certain bacteria (Clostridiales) at diagnosis correlated with the persistence of TRAb more than 200 days after commencing antithyroid drug treatment., Conclusion: The increased F:B ratio observed in GD/GO mirrors our finding in a murine model comparing TSHR-immunized with control mice. We defined a microbiome signature and identified changes associated with autoimmunity as distinct from those due to hyperthyroidism. Persistence of TRAb is predictive of relapse; identification of these patients at diagnosis, via their microbiome, could improve management with potential to eradicate Clostridiales., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Endocrine Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Autoimmune thyroid diseases (AITDs) are chronic autoimmune disorders that cause impaired immunoregulation, leading to specific immune responses against thyroid antigens. Graves' disease (GD) and Hashimoto's thyroiditis (HT) are the major forms of AITDs. Increasing evidence suggests a possible role of microbiota alterations in the pathogenesis and progression of AITDs. This systematic review was designed to address the following question: "Is microbiota altered in patients with AITDs?" After screening the selected studies using the inclusion and exclusion criteria, 16 studies were included in this review (in accordance with PRISMA statement guidelines). A meta-analysis revealed that patients with HT showed significantly higher values of diversity indices (except for the Simpson index) and that patients with GD showed significant tendencies toward lower values of all assessed indices compared with healthy subjects. However, the latter demonstrated a higher relative abundance of Bacteroidetes and Actinobacteria at the phylum level and thus Prevotella and Bifidobacterium at the genus level, respectively. Thyroid peroxidase antibodies showed the most significant positive and negative correlations between bacterial levels and thyroid functional parameters. In conclusion, significant alterations in the diversity and composition of the intestinal microbiota were observed in both GD and HT patients.

Background: Graves' disease is one of the most common autoimmune conditions, but treatment remains imperfect. This study explores the first-in-human use of antigen-specific immunotherapy with a combination of two thyrotropin receptor (TSHR) peptides (termed ATX-GD-59) in Graves' hyperthyroidism. Methods: Twelve participants (11 female) with previously untreated mild to moderate Graves' hyperthyroidism were enrolled in a Phase I open label trial to receive 10 doses of ATX-GD-59 administered intradermally over an 18-week period. Adverse events, tolerability, changes in serum free thyroid hormones, and TSHR autoantibodies were measured. Results: Ten subjects received all 10 doses of ATX-GD-59, five (50%) of whom had free triiodothyronine within the reference interval by the 18-week visit. Two further subjects had improved free thyroid hormones by the end of the study (7/10 responders), whereas three subjects showed worsening thyrotoxicosis during the study. Serum TSHR autoantibody concentrations reduced during the study and correlated with changes in free thyroid hormones ( r  = 0.85, p  = 0.002 for TSHR autoantibody vs. free triiodothyronine). Mild injection-site swelling and pain were the most common adverse events. Conclusions: These preliminary data suggest that ATX-GD-59 is a safe and well-tolerated treatment. The improvement in free thyroid hormones in 70% of subjects receiving the medication suggests potential efficacy as a novel treatment for Graves' hyperthyroidism.

Competing Interests: The authors have read and understood The BMJ Education policy on declaration of interests. The BMJ has judged that there are no relevant competing financial interests. The authors declare the following other interests: Lakdasa Premawardhana has received funding from the World Bank for a study examining “The emergence of thyroid autoimmunity following universal salt iodisation” (completed and data analysed and presented in Sri Lanka). LP has contributed to educational events for the European Federation of Laboratory Medicine and Clinical Chemistry in Amsterdam, March 2017, and on the topics “thyroid testing during acute illnesses” and “anomalous thyroid results in clinical practice” for the Sri Lanka Medical Association in Colombo, July 2017 Ilaria Muller has received an early career grant from the Society for Endocrinology (SfE), UK. IM has contributed to educational events on the topics “thyroid autoimmunity and breast cancer” for the 15th International Thyroid Congress (ITC) in Orlando, Florida, USA, 2015; on the topic “alemtuzumab-induced thyroid autoimmunity” for the British Thyroid Association (BTA) annual meeting in London, May 2017; and on the topic “alemtuzumab-induced thyroid autoimmunity” for the European Thyroid Association (ETA) annual meeting in Belgrade, Serbia, Sep 17. She received expenses from these companies for these events and a Society for Endocrinology (SfE) Travel Grant to attend the Society for Endocrinology (SfE) meeting in Harrogate, UK, 6-8 November 2017.