Free thyroxine abbreviated as FT4, high value can be a physiological phenomenon, such as women during pregnancy and lactation due to large fluctuations in hormone regulation, but also seen in thyroid disease. Clinically, it needs to be combined with other thyroxine tests to diagnose the disease: I. Generating factors: 1. Pregnancy and lactation: Due to the influence of placental hormones and neuroendocrine, the hormone levels in pregnant women fluctuate to adapt to the needs of fetal growth and development. FT4 in serum is mildly elevated from 5-9 weeks of pregnancy and peaks together with HCG, then drops to normal levels. Lactating women can also have a temporary increase in FT4 due to the secretion of milk; 2. Hyperthyroidism: FT4 is not affected by thyroxine tuberculin and is more sensitive to the diagnosis of hyperthyroidism, if FT4 is elevated, the patient needs to be considered to have hyperthyroidism; 3. Abnormal thyroid function: commonly seen in thyroid cysts, thyroid hormone insensitivity signs, etc. Because only FT4 can enter tissue cells to play a physiological role, FT4 has more value in determining thyroid function and is more sensitive to abnormal thyroid conditions; 4. Other thyroid diseases: initial Hashimoto’s thyroiditis, thyrotoxicosis, etc. Patients need to go to the hospital to complete a thorough examination before diagnosis can be made. Second, treatment measures: 1, drug therapy: commonly used drugs including propylthiouracil, methimazole, methimazole and carbimazole, etc., for patients with mild to moderate enlargement of the thyroid gland; 2, puncture drainage: mainly for thyroid cysts, if the patient’s condition is serious, and there is swelling of the neck, breath-holding, swallowing difficulties, hoarse voice and other symptoms, you can take a thyroid puncture to drain the cyst fluid and relieve symptoms; 3 , surgical treatment: for patients with moderate or severe hyperthyroidism, long-term medication ineffective, or relapse when medication is stopped, and those who cannot adhere to medication. In addition, if thyroid cancer is confirmed by fine needle aspiration cytology or suspected malignancy, subtotal or total resection is also feasible. 4. Radiotherapy: Radioactive 131 treatment can destroy follicular epithelium and reduce the secretion of thyroid hormones.