Autoimmune thyroid disease (AITD), which includes Hashimoto's thyroiditis (HT) and Grave's disease (GD), are the most common organ-specific autoimmune diseases and affect more women than men, with a female-to-male ratio from 5 to 10. Many studies have indicated that alterations in the gut microbiota are important environmental factors in the development of inflammatory and autoimmune diseases. Investigators systematically performed a comparative analysis of the gut microbiota in AITD patients and healthy controls.

Autoimmune thyroid disease (AITD), which includes Hashimoto's thyroiditis (HT) and Grave's disease (GD), are the most common organ-specific autoimmune diseases and affect more women than men, with a female-to-male ratio from 5 to 10. These two diseases are clinically diverse because in HT, T cells aid in the destruction of the thyroid epithelial cells (thyrocytes) and thyroid epithelial structure and eventual fibrous replacement of parenchymal tissue leading to hypothyroidism, whereas GD is primarily a humoral disease where auto-antibodies are generated against the thyroid stimulating hormone receptor (TSHR) leading to hyperthyroidism (2,163-165). However, these diseases still share several immunological features，and the disease may progress from one state to another as the autoimmune process evolves. Many studies have indicated that alterations in the gut microbiota are important environmental factors in the development of inflammatory and autoimmune diseases. Investigators systematically performed a comparative analysis of the gut microbiota in AITD patients and healthy controls.

Inclusion Criteria:

• Aged 18 to 65 years
• Male or female gender
• Euthyroidism (normal FT3, FT4, and TSH plasma levels without hormonal therapy)

Exclusion Criteria:

• Pregnancy
• Lactation
• Cigarette smoking
• Alcohol addiction
• Hypertension
• Diabetes mellitus
• Lipid dysregulation
• BMI > 27
• Recent (< 3 months prior) use of antibiotics, probiotics, prebiotics, symbiotics, hormonal medication, proton pump inhibitors, insulin sensitizers or Chinese herbal medicine
• Known history of disease with an autoimmune component such as MS, rheumatoid arthritis, IBS, and IBD
• History of malignancy or any gastrointestinal tract surgery (e.g., gastrectomy, bariatric surgery, colectomy, ileectomy, cholecystectomy or appendectomy).

Study Population are aged from 18 to 65 years，which divided into 4 groups:treatment-naive HT, treatment-naive GD, GD treated, healthy controls.