The thyroid gland is the only one of all endocrine glands that can be seen by the naked eye or can be palpated. Commonly used ancillary tests are briefly described as follows: 1. Thyroid function tests include: thyroid serological tests: T3, T4, FT3, FT4, TSH, rT3; clinically, TT4 and TT3 are affected by the level of thyroid hormone-binding globulin, and TSH test results are affected by the concentration of antibodies, and the results should be analyzed in conjunction with clinical and immunological indicators. rT3 is clinically significant for low rT3 has significance for the diagnosis of low T3 syndrome. 2. Thyroid 131I uptake rate: The functional status of the thyroid gland is judged by the entry of inorganic iodine into the thyroid gland, which is poor for the diagnosis of hypothyroidism. However, iodide is visible in breast milk and can pass through the placenta, so it is contraindicated during pregnancy and breastfeeding. 3.Dynamic tests such as TRH excitation and T3 inhibition test: TRH excitation test is valuable to distinguish whether the cause of secondary hypothyroidism is in the hypothalamus or pituitary gland; T3 inhibition test is good for the diagnosis of hyperthyroidism, but it is easy to cause adverse reactions in the elderly and people with cardiovascular disease, so the test should be avoided as much as possible for them. 4.High-sensitivity thyrotropin immunoradiometric assay (H-TSH IRMA): Some authors believe that it can be the first choice for thyroid function tests, but this view is not generally accepted. 5. Bismuth perchlorate excretion test: This test can be used to determine the degree of iodine organicization disorder in the thyroid gland by measuring the change of 131I uptake in the thyroid gland after taking perchlorate. 10% indicates iodine organicization disorder in the thyroid gland, and this test is useful for “familial iodine organicization disorder in the thyroid gland” and “chronic lymphocytic thyroiditis”. This test is useful in the diagnosis of “familial thyroid iodine organic disorder” and “chronic lymphocytic thyroiditis”, and has been performed in our hospital. 6. Indirectly, thyroid function can be reflected by evidence of metabolic disorders such as blood count, sedimentation, glucose, electrolytes, ions, and lipids. 2. Morphology, structure and tissue examination of the thyroid gland: 1. Ultrasound examination: It can show the morphology, size and structure of the thyroid gland. A high-resolution ultrasound can distinguish nodules with a diameter of 0.5 cm or more. However, ultrasound has certain limitations, it can only determine the existence of the mass and distinguish whether the mass is solid, cystic or mixed, but not qualitative. Therefore, it is easy to misdiagnose subacute thyroiditis (often manifested as a thyroid mass) as a thyroid adenoma in clinical practice. 2. Radionuclide scan of thyroid gland: The main function of radionuclide scan is to distinguish between “cold”, “warm” and “hot” thyroid nodules. 2. X-rays: X-rays of the neck can be used to observe calcified foci in the gland and whether the trachea is displaced by pressure. The rate of calcification in thyroid cancer is reported to be high, but it is difficult to determine the benignity and malignancy by X-ray, so it is not used nowadays. 4.CT and MRI of the neck: It can clarify the relationship between the thyroid gland, its swelling and the adjacent tissues. Thin layer and dynamic enhancement scans can be used for clearer visualization. 5.Thyroid puncture biopsy or fine needle aspiration cytology: ultrasound-guided tissue biopsy is safe and easy, and the sensitivity and specificity for distinguishing benign and malignant lesions of the thyroid gland are above 85%. However, it has not been carried out in our hospital yet. There are many autoantibodies in the thyroid gland, and their existence is an important sign of autoimmune dysfunction of the body. The following are commonly detected clinically: 1. They can also be seen in the same patient at the same time or in different stages, and the current tests cannot distinguish between them. This antibody test is useful in the diagnosis of Graves’ disease, i.e., hyperthyroidism and evaluation after gas medication. 2. TG-Ab (thyroglobulin antibody) 3. thyroid peroxidase antibody (TPO-Ab) The clinical significance of TG-Ab and TPO-Ab is the same. Note: Not all patients with chronic lymphocytic thyroiditis have high thyroid autoantibodies. Although adjuvant tests currently play an important role in the diagnosis of thyroid disease in clinical practice, after all, one cannot rely on adjuvant tests alone to obtain a correct diagnosis, so clinical practice also requires a combination of medical history (e.g., acute and subacute thyroiditis often have a history of upper respiratory tract infection), symptoms, and signs. (The classification of thyroid diseases will be introduced later.)