It occurs when an overactive thyroid leads to hypermetabolism, which can cause death from cardiac arrest or multiple organ failure.

[2] It is characterized by a high fever (temperatures often above 40 °C / 104 °F), fast and often irregular heart beat, elevated blood pressure, vomiting, diarrhea, and agitation.

[9][10] Thyroid storm is characterized by an acute onset of symptoms of hyperthyroidism (fast heart rate, restlessness, agitation) accompanied by other features such as fever (temperatures often above 40 °C/104 °F), hypertension, mental status changes, diarrhea, and vomiting.

Patients may experience liver dysfunction, and jaundice (yellowing of the skin), which is considered a poor prognostic sign.

[11] The transition from hyperthyroidism to thyroid storm is typically triggered by a non-thyroidal insult including, but not limited to fever, sepsis, dehydration, myocardial infarction, and psychiatric diseases.

[vague][13][14] Individuals are at higher risk of thyroid storm if their hyperthyroidism is incompletely treated or if their anti-thyroid drugs are discontinued.

However, thyroid storm can occur in individuals with unrecognized thyrotoxicosis experiencing non-thyroid surgery, labor, infection, or exposure to certain medications and radiocontrast dyes.

[15] Sympathetic nervous system activation during times of stress may also play a significant role in thyroid storm.

This is likely responsible for several of the cardiovascular symptoms (increased cardiac output, heart rate, stroke volume) seen in thyroid storm.

[15] Multiple approaches have been proposed to calculate the probability of thyroid storm based on clinical criteria, however, none have been universally adopted by clinicians.

[21] In cases of heart failure leading to hemodynamic collapse, cardiocirculatory support including VA-ECMO may be required.

[25] The administration of beta-1-selective beta blockers (e.g. metoprolol) is recommended to reduce the effect of circulating thyroid hormone on end organs.

[4][21][6] Propranolol at high doses is a common first-line treatment, as it reduces peripheral conversion of T4 to T3, which is the more active form of thyroid hormone.

[27] Guidelines recommend that corticosteroids (hydrocortisone and dexamethasone are preferred over prednisolone or methylprednisolone) be administered to all patients with thyroid storm.

However, doses should be altered for each individual patient to ensure that the relative adrenal insufficiency is adequately treated while minimizing the risk of side effects.

Supportive measures include treatment of precipitating factors (e.g. infection), intravenous fluids, and cooling blankets and ice packs for persistent fever.

Extracorporeal membrane oxygenation (ECMO) can be used as a bridging measure for refractory cardiorespiratory failure induced by thyroid storm.