If hyperthyroidism is not treated in time, it can easily lead to various complications. The main complications that can be caused by hyperthyroidism include hyperthyroid heart disease, hyperthyroid eye disease, hyperthyroid myopathy, hyperthyroid periodic paralysis and so on. In serious cases, hyperthyroidism can lead to hyperthyroid crisis, which is often life-threatening if not rescued. 1. Hyperthyroid heart disease Hyperthyroid heart disease refers to patients with hyperthyroidism who have arrhythmia, heart enlargement, or heart failure, and it is more common in patients with a long history of uncontrolled hyperthyroidism and in the elderly. In addition to the typical clinical manifestations of hyperthyroidism, the disease is often associated with palpitations, dyspnea, precordial pain, premature beats (premature beats) or paroxysmal atrial fibrillation, and even persistent atrial fibrillation. The main treatment is to control the hyperthyroidism, and if heart failure and arrhythmia appear, symptomatic treatment can be given, and the hyperthyroidism can generally be completely restored to normal after it is well controlled. 2. Hyperthyroidism proptosis Hyperthyroidism proptosis can occur at the same time as hyperthyroidism, or it can occur before hyperthyroidism or after it gets better. The severity of ophthalmoplegia and hyperthyroidism are not parallel in most cases, and in some patients, hyperthyroidism is not obvious but ophthalmoplegia is very serious. It can be divided into non-infiltrative proptosis and infiltrative proptosis. The former manifests as widening of the eye fissure, eyelid retraction, gaze, reduced blinking and mild proptosis; the latter may manifest as excessive tearing, photophobia, eye swelling, stinging pain, foreign body sensation, inability to close the eye, conjunctival edema and congestion, orbital tissue edema, limited eye movement, double vision, visual field defects, reduced visual acuity and even blindness. For benign proptosis, no special treatment is needed, only treatment of hyperthyroidism is sufficient. Infiltrative cases can be treated with antithyroid drugs along with adrenal glucocorticoids, and a few need to be treated with ocular radiation therapy or ocular surgery. No matter which treatment is used, it is important to take good care of the eyes during the treatment period. Eye care includes elevating the head of the bed when sleeping, wearing sunglasses to avoid light and dust when going out, and applying eye drops, eye ointment or wearing eye shields. 3, chronic hyperthyroidism myopathy This disease is more common and can occur in 80% of hyperthyroid patients, with a slow onset. Patients often complain of difficulty in squatting, standing up, going upstairs and combing their hair. Treatment is mainly for hyperthyroidism and there is no specific treatment yet except for symptomatic management. It can generally be reduced with the remission of hyperthyroidism. 4, hyperthyroidism combined with periodic paralysis This disease occurs mostly in male young adults, the attack is often accompanied by low blood potassium, high carbohydrate diet can trigger the disease, often in the middle of the night attack. The main manifestation is episodic flaccid paralysis of the limbs and trunk, with lower limb paralysis being more common. The frequency of attacks varies greatly among individuals. The disease may be related to intracellular transfer of potassium from cells. Treatment is mainly potassium supplementation. For patients without previous history of hyperthyroidism, if paralysis due to low potassium occurs, it is important to clarify whether hyperthyroidism is present. 5. Hyperthyroidism crisis Hyperthyroidism crisis is common in people with uncontrolled hyperthyroidism for a long time, and is more common in the elderly. It is often associated with infection, trauma, surgery, childbirth, overexertion, and sudden discontinuation of medication. The main manifestations are high or ultra-high fever (often higher than 40℃), increased pulse rate (often higher than 160 beats/min), irritability, nausea, vomiting, diarrhea, profuse sweating, excitement and trembling, and even hazy consciousness and coma. The disease can be life-threatening and has a high mortality rate. Prevention should be the main focus, and once detected, it should be actively treated. The principle of treatment is to inhibit the production and secretion of thyroid hormones with medication, reduce the response of brain and surrounding tissues to thyroid hormones and general symptomatic treatment. In addition, complications of hyperthyroidism include acute hyperthyroid myopathy, hyperthyroid hypertension, hyperthyroid psychosis, and anterior tibial mucinous edema, all of which are rare, and if they occur, they need to be promptly treated at a hospital.