Hyperthyroidism and hypothyroidism are two different diseases, and there is no such thing as which one is more serious. Both diseases can lead to more serious consequences if not actively treated. 1. Hyperthyroidism is a group of clinical syndromes caused by the thyroid gland synthesizing and releasing too much thyroid hormone. Typical manifestations are fear of heat, excessive sweating, excessive eating, panic, weight loss, emaciation and so on. If no intervention is given, it may cause serious complications such as hyperthyroidism heart disease, hyperthyroidism crisis, and even death. 2. Hypothyroidism is also called hypothyroidism, and its causes include autoimmune thyroiditis. Typical symptoms include decreased eating, weakness and chills, and other hypometabolic symptoms. It is mainly caused by the low synthesis and secretion of the thyroid gland. If it is not treated actively, it may cause complications such as coma and pericardial effusion, which will seriously affect your health. Therefore, both hyperthyroidism and hypothyroidism need to be taken seriously, and timely medical treatment should be sought at the early stage of the disease to effectively control the condition through active intervention.