In the clinic, I met an elderly female diabetic patient who said she had recently gained weight and always felt cold, and was very confused. I examined her carefully and found that her thyroid gland was enlarged, her serum FT3 and FT4 were decreased, and her TSH was increased. Hypothyroidism, referred to as “hypothyroidism”, is an endocrine disorder caused by insufficient synthesis or secretion of thyroxine by the thyroid gland or a lack of responsiveness to thyroid hormones in the surrounding tissues. In fetal, neonatal and early childhood, hypothyroidism is characterized by low basal metabolic rate, slow growth, short bones, dwarfism, mental retardation, coldness and sluggishness, which is called cretinism; in adult, it is characterized by coldness, lassitude, hoarseness, unresponsiveness, dry skin, swollen eyes and cheeks, poor appetite, bloating, constipation, weight gain and slow heart rate. The basic manifestations of the disease include In severe cases, pericardial effusion, amenorrhea, lactation, impotence, drowsiness, and even lethargy may occur. There are many different causes of hypothyroidism, so the treatment and prognosis are different. In hypothyroidism, the TSH, T3, T4, FT3, FT4 of the pituitary gland is significantly higher than normal, the T4 and FT4 of the thyroid gland are lower than normal, and the T3 and FT3 are normal in mild cases, but significantly lower in severe cases. In some hypothyroid patients without any symptoms, only TSH may be elevated in the blood. In a few patients, the lesion is not in the thyroid gland but in the pituitary gland or hypothalamus, in which case both TSH and thyroid hormones are reduced in the blood. In patients with Hashimoto’s thyroiditis, thyroid-specific antibodies TGAb and TPOAb may be elevated. Hypothyroidism should be differentiated from nephrogenic edema, anemia, and congestive heart failure. Hypothyroidism and overflow symptoms should be differentiated from lactinoma. Most hypothyroidism is a permanent disease that requires lifelong medication. Only a small percentage of hypothyroidism such as subacute thyroiditis and drug-induced hypothyroidism can be cured after treatment. The main treatment for hypothyroidism is thyroxine hormone replacement therapy. At present, dry thyroid tablets and levothyroxine tablets (euthyroxine) are commonly used in China, which have satisfactory effects and are cheap and simple to take. The dosage should be increased gradually according to the systemic symptoms and laboratory tests until the systemic symptoms disappear and T3, T4, FT3, FT4 and TSH return to normal. Thereafter, maintain this dose for life and do not stop taking the drug easily, otherwise, the symptoms that disappeared may appear again within 1 to 3 months. In addition, even if all the symptoms disappear after taking the medication, the thyroid hormone level in the body should be rechecked regularly at the hospital, and the medication dose should be adjusted appropriately according to the test results, usually once every six months to a year. Some patients with hypothyroidism also need to undergo etiological treatment. If hypothyroidism is caused by iodine deficiency, iodine supplementation should be given; if hypothyroidism is caused by high iodide, iodide should be stopped; if hypothyroidism is caused by drugs, it can disappear by itself after reducing or stopping the dosage; if hypothyroidism occurs in 3-4% of psychiatric patients treated with lithium salt, it can be improved by stopping the drugs; if there is a large tumor in hypothalamus or pituitary gland, hypothyroidism may be improved to different degrees after performing tumor resection. Many hypothyroid patients ask what they should pay attention to in their diet after suffering from hypothyroidism. 1, limit fat intake: fat is the body supply of heat and help fat-soluble vitamin absorption substances. In hypothyroidism, plasma cholesterol is excreted slowly, so the concentration of plasma cholesterol is very high. The intake of fat should be limited to reduce the concentration of plasma cholesterol. 2. Iodized salt supplementation: This iodized salt is extremely suitable for endemic goiter areas. Women during childbirth should pay more attention to iodized salt supplementation to prevent their offspring from developing cretinism due to maternal iodine deficiency. However, some patients with hypothyroidism are caused by excessive iodine intake and should not be treated as such. For hypothyroidism caused by Hashimoto’s thyroiditis, excessive intake is not recommended because excessive iodine intake can raise thyroid autoantibodies (TPOAb, TGAb), thus aggravating thyroiditis; for hypothyroidism caused by isotope treatment of hyperthyroidism, as long as the thyroid hormone receptor antibody (TRAb) is still positive, strict avoidance of iodine is still recommended. 3. Supply enough protein: Therefore, you should consume more eggs, dairy, meat and fish, and pay attention to the complementarity of vegetable and animal proteins.