Thyroid storm: emergency signs, triggers and hospital treatment

Thyroid storm is the most extreme form of an overactive thyroid: hormone levels overwhelm the body and organs start to fail. It is rare, but even with hospital treatment about 1 in 10 people with it die, so the main thing to know is how to recognise it and when to get help.

Key points

• Signs: rapid heartbeat, high fever, high blood pressure, jaundice, severe agitation or confusion, collapse.
• Triggers: infection, pregnancy, not taking antithyroid medicine properly, injury to the thyroid.
• Rare: about 0.2 per 100,000 hospital patients a year in a Japanese survey.
• Serious: death rates of about 10% to 11% in Japan and about 8% at 90 days in Taiwan.
• Prevention: take carbimazole as prescribed and do not stop it suddenly.

Warning signs

The NHS lists:

• a rapid heartbeat
• a high temperature
• high blood pressure
• yellowing of the skin and eyes (jaundice)
• severe agitation and confusion
• loss of consciousness

Japanese diagnostic criteria built from nationwide surveys add heart failure and gut or liver problems, such as vomiting, diarrhoea and jaundice, to the brain, fever and heart-rate signs. The hormone levels themselves are often no higher than in people with an ordinary overactive thyroid; the difference is the body’s reaction.

What triggers it

The NHS names infection, pregnancy, not taking medicine correctly, and damage to the thyroid gland, such as a blow to the throat. The British Thyroid Foundation notes that radioactive iodine given to a very overactive gland can, very rarely, cause a thyroid crisis, which is why doctors usually control levels with carbimazole first.

How hospitals treat it

There are no large trials, because the condition is rare. The 2016 Japanese guideline, based on 356 patients from nationwide surveys and the literature, recommends combined treatment, usually in intensive care:

• an antithyroid drug (methimazole or PTU) to stop new hormone being made
• inorganic iodide to block hormone release
• corticosteroids
• a beta blocker to slow the heart

plus treatment of the trigger and support for failing organs. In the Japanese survey, methimazole was used in most patients and did no worse than PTU. Patients given non-selective beta blockers had higher mortality than those given other types. PTU also blocks the conversion of T4 into the more active T3, which its US label notes may make it effective in thyroid storm.

Multiple organ failure was the most common cause of death, followed by heart failure, respiratory failure and arrhythmia.

After recovery

Once someone has survived thyroid storm, a definitive treatment such as radioactive iodine or surgery is usually discussed, so the thyroid cannot flare again. See radioactive iodine and thyroid surgery.

Preventing it

• Take carbimazole or methimazole every day as prescribed and keep up blood tests.
• Order repeat supplies early: carbimazole is listed by PockDose, Yasabai and VGR Australia.
• Get infections treated promptly and tell the doctor about your thyroid condition.
• Tell your doctor straight away if you become pregnant.

More on hyperthyroidism and dosage.

Sources

Checked 15 October 2026.

1. Overactive thyroid (hyperthyroidism), complications — NHS (UK)
2. 2016 guidelines for the management of thyroid storm from the Japan Thyroid Association and Japan Endocrine Society (Satoh et al.) — Endocrine Journal
3. Diagnostic criteria, clinical features and incidence of thyroid storm based on nationwide surveys (Akamizu et al., 2012) — Thyroid
4. Treatment and management of thyroid storm: analysis of the nationwide surveys (Isozaki et al., 2016) — Clinical Endocrinology
5. Epidemiology and factors associated with mortality of thyroid storm in Taiwan (2021) — Internal and Emergency Medicine
6. Propylthiouracil tablets prescribing information (clinical pharmacology) — DailyMed, US National Library of Medicine
7. Treatment of an overactive or enlarged thyroid gland with radioactive iodine (patient leaflet) — British Thyroid Foundation