Hypothyroidism occurs when the thyroid gland is unable to produce sufficient amounts of thyroid hormones to supply the body with what it needs. The main causes of hypothyroidism are thyroidectomy, sequelae of radioactive iodine treatment, destruction of the thyroid gland due to thyroiditis, congenital thyroid deficiency, and ectopic thyroid. The symptoms of hypothyroidism are the opposite of hyperthyroidism. It mainly causes the body’s metabolic rate to decrease and all cellular activities to slow down. Patients may show loss of appetite, fear of cold, dry and rough skin, brittle hair, fatigue, constipation, and even muscle weakness and a low, hoarse voice. Physical examination may reveal a slowed pulse, edema of the eyelids, pale face, slightly yellow skin, and memory loss. Clinical treatment of hypothyroidism mainly uses synthetic thyroid hormones (such as eugenol, thyroxine tablets, etc.), which generally do not cause side effects and rarely cause allergic reactions, and the dosage varies from person to person. Regular blood tests are required to monitor the adequacy of the medication while taking it. Since hypothyroidism is often caused by irreversible or permanent damage, most hypothyroid patients need to take thyroid hormone therapy for life and cannot stop taking it arbitrarily, especially during pregnancy when the mother’s need for thyroid gland increases and if the supplementation is insufficient, it will affect the growth of the fetus.