Hyperthyroidism may cause the patient’s body temperature to rise, and in the case of a thyroid crisis, a high or excessive fever may occur. Hyperthyroidism is a form of thyrotoxicosis due to the production of too much thyroid hormone by the glands of the thyroid gland. The main manifestation is hypermetabolic syndrome, which is due to the increased production of thyroid hormones, resulting in an accelerated metabolism and elevated sympathetic excitability. Common manifestations of hyperthyroidism include agitation, irritability and insomnia, palpitations, fatigue, fear of heat, excessive sweating, lethargy, hyperphagia, increased frequency of bowel movements or diarrhea, and scanty menstruation in women. In the presence of thyroid crisis, a large amount of thyroid hormone enters the circulation, resulting in possible clinical manifestations such as high or excessive fever, profuse sweating, tachycardia, irritability, and anxiety. Patients with hyperthyroidism should follow the doctor’s instructions for treatment, and go to a regular medical institution in time when discomfort occurs, so as not to miss the condition.