The main causes of hypothyroidism include autoimmune damage, thyroid destruction, antithyroid medications, lesions of the pituitary gland or hypothalamus, and other causes. 1. Autoimmune damage: autoimmune diseases such as Hashimoto’s thyroiditis and atrophic thyroiditis may cause damage to thyroid cells and tissues. 2. Thyroid destruction: e.g. thyroidectomy, radioactive iodine treatment, etc. 3. Antithyroid drugs: such as thioureas, imidazoles, etc. Improper use of drugs may lead to hypothyroidism. 4. Pituitary or hypothalamic lesions: the pituitary gland and the hypothalamus regulate the function of the thyroid gland. Pituitary tumors, pituitary damage or hypothalamic lesions may lead to hypothyroidism. 5. Other factors: congenital absence or ectopic thyroid gland, postpartum thyroiditis, hypothyroidism and so on. Patients with hypothyroidism should consult a doctor in time to complete the relevant examinations.