TG and Hashimoto thyroiditis: In patients with Hashimoto’s thyroiditis, a decline in Faecalibacterium prausnitzii abundance has been noted with an inverse correlation between Faecalibacterium’s relative abundance and thyroid autoantibodies or the FT3 to FT4 ratio, underscoring a close association with thyroid hormones and their functionality (21, 68, 69).