Thyroid Storm (Thyrotoxic Crisis)

What happens in thyroid storm

Thyroid hormones speed up the metabolism of almost every cell. In thyroid storm, a trigger in someone who is already thyrotoxic causes a sudden worsening, with increased sensitivity of the body to the hormone. Heart rate, temperature and energy use soar, and the heart, brain, liver and gut start to fail.

Thyroid storm is rare, affecting a small fraction of people hospitalized with thyrotoxicosis, but mortality is about 10% or higher even with treatment.

Causes and triggers

Underlying conditions

• Graves' disease (most common)
• Toxic multinodular goiter
• Toxic adenoma
• rarely, thyroiditis or excess thyroid hormone tablets

Triggers

• infection, the most common trigger
• surgery, especially thyroid surgery in an uncontrolled patient
• trauma
• childbirth, preeclampsia
• stopping antithyroid medicine
• radioactive iodine treatment without preparation
• iodine load from CT contrast or amiodarone
• diabetic ketoacidosis, heart attack, stroke, pulmonary embolism

Symptoms

• high fever, often over 38.5 °C (101.3 °F) and sometimes much higher
• very fast heart rate, often over 140 beats a minute, and atrial fibrillation
• heart failure: breathlessness, swelling
• nervous system: agitation, anxiety, delirium, psychosis, seizures, coma
• gut and liver: nausea, vomiting, diarrhea, abdominal pain, jaundice
• heavy sweating, tremor and dehydration

Older people may instead show "apathetic" features such as weakness and lethargy.

Diagnosis

Thyroid storm is a clinical diagnosis, because hormone levels are often no higher than in ordinary hyperthyroidism. Doctors use:

• Burch-Wartofsky Point Scale: scores temperature, nervous system effects, gut and liver dysfunction, heart rate, heart failure, atrial fibrillation and a trigger. A score of 45 or more strongly suggests thyroid storm
• Japanese Thyroid Association criteria
• thyroid tests: suppressed TSH, high free T4 and T3
• tests for the trigger: blood cultures, chest X-ray, ECG, liver and kidney function, glucose, pregnancy test

Treatment should start without waiting for test results.

Treatment

Management is in an intensive care unit and targets each step of thyroid hormone action:

1. Beta-blockers (often propranolol) to control heart rate and symptoms, with caution in heart failure
2. Thionamides: propylthiouracil (PTU) or methimazole to block new hormone production. PTU also reduces conversion of T4 to the more active T3
3. Iodine (potassium iodide or Lugol's solution), given at least an hour after the thionamide, to block hormone release
4. Glucocorticoids (hydrocortisone or dexamethasone) to reduce T4 to T3 conversion and treat possible adrenal insufficiency
5. Supportive care: IV fluids, cooling blankets, acetaminophen (paracetamol) for fever, nutrition, oxygen. Avoid aspirin, which can increase free thyroid hormone
6. Treat the trigger, such as infection
7. Other options: cholestyramine to reduce hormone recycling, plasmapheresis or urgent thyroidectomy in refractory cases

Complications

• heart failure and cardiogenic shock
• arrhythmias and stroke
• multi-organ failure
• death

After recovery

Once stable, definitive treatment of the underlying hyperthyroidism is planned with radioactive iodine or surgery, after the thyroid is controlled with medicine. Lifelong follow-up is needed, often with thyroid hormone replacement afterward.

Prevention

• take antithyroid medicine as prescribed and do not stop suddenly
• get hyperthyroidism controlled before elective surgery or radioactive iodine
• seek early care for infections if you have an overactive thyroid
• tell clinicians about your thyroid condition before procedures with iodine contrast

Frequently asked questions

What is thyroid storm?

Thyroid storm is a rare, life-threatening worsening of hyperthyroidism. It causes high fever, a very fast heartbeat, confusion or agitation, vomiting and diarrhea, and can lead to heart failure and death without urgent treatment.

What triggers a thyroid storm?

Common triggers are infection, surgery, trauma, childbirth, stopping antithyroid medicine, radioactive iodine treatment and large iodine exposures such as CT contrast. It usually occurs in people with untreated or poorly controlled Graves' disease or toxic nodules.

What are the warning signs of thyroid storm?

Warning signs in someone with an overactive thyroid include fever, a heart rate over about 130 to 140, new irregular heartbeat, agitation, confusion, severe vomiting or diarrhea, and yellow skin. These need emergency care.

How is thyroid storm treated?

It is treated in intensive care with beta-blockers to slow the heart, antithyroid drugs to stop hormone production, iodine to block hormone release, steroids, cooling and fluids, and treatment of the trigger.

Can thyroid storm be prevented?

Most cases can be prevented by treating hyperthyroidism, taking antithyroid medicine consistently, getting the thyroid under control before surgery or radioactive iodine, and seeking prompt treatment for infections.