Primary hypothyroidism 1. Hypothyroidism caused by chronic lymphatic thyroiditis accounts for the majority of primary hypothyroidism. 2, Medical hypothyroidism (antithyroid drugs, radioactive iodine, thyroid surgery). 3.Postpartum thyroiditis or hypothyroidism caused by painless thyroiditis. 4. Hypothyroidism caused by endemic iodine deficiency. 5, Hormone synthesis disorder hypothyroidism. Congenital hypothyroidism. Secondary hypothyroidism Secondary hypothyroidism is caused by pituitary and/or hypothalamic lesions leading to a decrease in thyroid stimulating hormone (TSH) and/or thyrotropin releasing hormone (TRH), including Sheehan’s disease, autoimmune pituitary inflammation, pituitary tumors, radiological pituitary inflammation, and hypothalamus and its peripheral tissues of the tumors, inflammation, degeneration, and hemorrhage, and so on. Peripheral hypothyroidism Peripheral hypothyroidism includes thyroid hormone receptor and post-receptor defects.