Common tests include thyroid function tests, thyroid autoantibody tests, blood biochemical tests, etc. 1. Thyroid function tests: increased serum thyroid hormone and thyroid stimulating hormone, decreased thyroxine and free thyroxine are the main indicators for the diagnosis of hypothyroidism. In severe cases sometimes serum triiodothyronine and free triiodothyronine are reduced. In subclinical hypothyroidism, however, only serum thyrotropin is elevated, but serum thyroxine or serum triiodothyronine is normal. 2. Thyroid autoantibodies: Positive serum thyroid peroxidase antibodies and anti-thyroglobulin antibodies suggest that hypothyroidism is due to autoimmune thyroiditis. 3, biochemical examination: serum triglycerides and total cholesterol are increased, high-density protein cholesterol is decreased, homocysteine is increased. And the hemoglobin mostly shows mild or moderate orthocytic orthochromic anemia. 4.Thyroid hormone releasing hormone stimulation test: It is mainly used to differentiate primary hypothyroidism from central hypothyroidism. After intravenous injection of T thyrotropin-releasing hormone, serum thyrotropin does not increase manifesting as pituitary hypothyroidism, delayed increase as hypothalamic hypothyroidism; further increase in serum thyrotropin on the increased base value indicates primary hypothyroidism. The presence or absence of hypothyroidism needs to be confirmed under the guidance of a physician.