Hypothyroidism, or hypothyroidism, is a clinical syndrome caused by a lack of thyroid hormones and a decrease in the metabolic activity of the body, and the onset of hypothyroidism in adults is called “adult hypothyroidism”, and in severe cases it is called “mucinous edema”. “If the disease develops during the embryonic period or infancy, it will seriously affect the brain and body growth and development, and become a demented dwarf, called “cretinism” or “cretinism”. Cretinism”. If it appears in childhood, it is called juvenile hypothyroidism; if it appears in adulthood, it is called adult hypothyroidism. 1. Classification: 1. primary hypothyroidism; 2. over 95% of hypothyroidism is caused by thyroid disease, mostly due to autoimmunity, thyroid surgery, 131I treatment; 3. central hypothyroidism; 4. TRH or TSH secretion is reduced due to hypothalamic or pituitary lesions. Hypothyroidism caused by reduced secretion of TRH or TSH and consequently reduced secretion of TH caused by hypothalamic or pituitary lesions; 5, issue hypothyroidism (tertiary hypothyroidism); 6, thyroid hormone resistance syndrome caused by impaired biological effect of TH in peripheral tissues. The primary hypothyroidism is mainly caused by the thyroid gland itself, such as congenital thyroid deficiency, thyroid atrophy, diffuse lymphocytic thyroiditis, thyroid destruction treatment, thyroid hormone synthesis disorder, etc. All belong to primary hypothyroidism. (2) Secondary hypothyroidism (hypothyroidism) is caused by hypothyroidism, mainly due to pituitary disease, hypothalamic syndrome, hypothalamic tumor, inflammation and other causes. This is one of the more common causes of hypothyroidism, and people should do their best to prevent it. 3, peripheral hypothyroidism This type of hypothyroidism is relatively rare and is a family genetic disease. This type of hypothyroidism is characterized by normal function of peripheral target tissues, but the receptor function in the nucleus is impaired, so the physiological effect on thyroid hormone is reduced. 4. TSH insensitivity syndrome This is a type of hypothyroidism mainly due to the resistance of the thyroid gland to thyroid stimulating hormones. This type of hypothyroidism is also one of the causes of hypothyroidism, so it should be taken seriously.