Currently, there is no evidence to suggest that patients with Hashimoto's thyroiditis cannot eat mutton, so it is permissible to eat mutton. Hashimoto's thyroiditis is a common autoimmune thyroid disease and the primary cause of hypothyroidism. Its onset is generally closely related to genetic factors, abnormal iodine metabolism, and immune function abnormalities. The pathological characteristics are mainly marked by significant infiltration of lymphocytes and plasma cells in the thyroid, as well as fibrosis of thyroid tissues. In terms of diet, patients with Hashimoto's thyroiditis need to strictly control their iodine intake.