Thyrotoxic Crisis (Thyroid Storm)

What happens in thyroid storm

Thyroid hormones set the body's metabolic rate. In hyperthyroidism, levels are too high, and many tissues become more sensitive to adrenaline. In thyroid storm, a trigger pushes this system past the point the body can compensate. Heat production soars, the heart is driven extremely hard, and the brain, gut and liver are affected. Hormone levels may be no higher than in ordinary hyperthyroidism: it is the body's response that defines storm.

Without treatment, thyroid storm has a high death rate. Even with intensive treatment, about 1 in 10 people die, mainly from heart failure, arrhythmias and multi-organ failure.

Causes and triggers

Underlying thyroid conditions

• Graves' disease: the most common cause
• toxic multinodular goiter and toxic adenoma
• thyroiditis, rarely
• excess thyroid hormone medicine, rarely

Common triggers

• infection, the most common trigger
• stopping antithyroid medicines suddenly
• surgery, especially thyroid surgery in poorly prepared patients
• childbirth and preeclampsia
• trauma
• iodine contrast used in CT scans, or amiodarone
• radioactive iodine treatment, rarely
• diabetic ketoacidosis, heart attack, stroke and pulmonary embolism

Symptoms

Diagnosis

Thyroid storm is diagnosed clinically. Treatment should not be delayed waiting for test results.

• Burch-Wartofsky Point Scale: scores temperature, nervous system effects, gut and liver involvement, heart rate, heart failure, atrial fibrillation and presence of a trigger. A score of 45 or more strongly suggests thyroid storm; 25 to 44 suggests impending storm.
• thyroid function tests: low TSH and high free T4 and/or T3
• tests for the trigger: blood count, cultures, chest X-ray, urine tests
• ECG and heart ultrasound
• liver function, glucose and electrolytes

Doctors also consider sepsis, heat stroke, stimulant toxicity and serotonin syndrome, which can look similar.

Treatment

Treatment is given in intensive care and works on several steps at once:

1. Block the effects of thyroid hormone: beta-blockers, usually propranolol, which also reduces conversion of T4 to the active T3. Short-acting esmolol may be used in heart failure.
2. Stop new hormone production: antithyroid drugs. Propylthiouracil is often preferred initially because it also blocks T4 to T3 conversion, and methimazole is an alternative.
3. Stop hormone release: iodine solution (such as potassium iodide), given at least 1 hour after the antithyroid drug.
4. Reduce conversion and support the adrenals: IV hydrocortisone.
5. Supportive care: cooling, IV fluids, glucose, oxygen and treatment of heart failure and arrhythmias. Acetaminophen (paracetamol) for fever. Aspirin is avoided because it can increase free thyroid hormone levels.
6. Treat the trigger, such as antibiotics for infection.

If medicines fail, plasma exchange or urgent thyroidectomy may be used.

After recovery

Once stable, definitive treatment of the overactive thyroid is planned, usually radioactive iodine or surgery, to prevent recurrence. Long-term thyroid hormone replacement is then often needed. See hyperthyroidism.

Prevention

• take antithyroid medicines regularly and do not stop without medical advice
• make sure hyperthyroidism is well controlled before planned surgery or childbirth when possible
• seek prompt care for infections if you have an overactive thyroid
• tell radiology staff about hyperthyroidism before iodine contrast scans

Frequently asked questions

What is thyroid storm?

Thyroid storm, or thyrotoxic crisis, is a rare and life-threatening complication of an overactive thyroid. The body is overwhelmed by thyroid hormone effects, causing high fever, a racing heart, agitation or confusion, and vomiting or diarrhea. It is a medical emergency.

What triggers a thyroid storm?

The most common trigger is infection. Others include stopping antithyroid medicines, surgery, childbirth, trauma, iodine contrast dye, radioactive iodine and serious illnesses such as heart attack or diabetic ketoacidosis, in people with untreated or poorly controlled hyperthyroidism.

What are the symptoms of thyroid storm?

Symptoms include high fever, heavy sweating, a very fast or irregular heartbeat, breathlessness, agitation, confusion, delirium, vomiting, diarrhea and sometimes yellow skin. Severe cases cause seizures, coma, heart failure and shock.

How is thyroid storm treated?

It is treated in intensive care with beta-blockers to control the heart rate, antithyroid medicines to stop hormone production, iodine to block hormone release, steroids, cooling and fluids, plus treatment of the trigger, such as an infection.

Can thyroid storm be prevented?

Usually, yes. Taking antithyroid medicine consistently, getting hyperthyroidism under control before surgery or delivery, and seeking early care for infections greatly reduce the risk. People with hyperthyroidism should not stop their medicine without medical advice.