An Overview of Thyroid Storm

Graves' disease is an autoimmune disease that typically causes hyperthyroidism, in which the thyroid gland produces too much thyroid hormone and becomes overactive. In 1 percent to 2 percent of cases, the thyroid produces an extreme amount of the key hormones involved in thyroid function—triiodothyronine (T3) and thyroxine (T4). This can cause your heart rate, blood pressure, and body temperature to become uncontrollably high—what's known as a thyroid storm. This is dangerous and potentially life-threatening.

The primary risk factor for thyroid storm is having untreated Graves' disease and/or hyperthyroidism. 

Even when the Graves' disease is identified and being treated, there are a number of other factors that raise your risk of thyroid storm:

• Infection, specifically lung infections, throat infections, or pneumonia
• Blood sugar changes, including diabetic ketoacidosis and insulin-induced hypoglycemia
• Recent surgery on your thyroid gland or trauma to your thyroid
• Abrupt withdrawal of your antithyroid medications
• Radioactive iodine (RAI) treatment of your thyroid
• Excessive palpation (handling/manipulation) of your thyroid gland
• Exposure to a large quantity of iodine (such as an iodine-based contrast agent or the heart drug amiodarone)
• Severe emotional stress
• An overdose of thyroid hormone drugs
• Toxemia of pregnancy and labor

Symptoms of thyroid storm are usually quite extreme and include:

• A very high fever of 100 to 106 degrees
• A very high heart rate, which can be as high as 200 beats per minute (BPM) 
• Palpitations, chest pain, and shortness of breath
• High blood pressure
• Confusion, delirium, and even psychosis
• Extreme physical and muscle weakness
• Extreme fatigue and exhaustion
• Extreme restlessness, nervousness, and mood swings
• Exaggerated reflexes, especially in knee and ankle areas
• Difficulty breathing
• Nausea, vomiting, and diarrhea
• Profuse sweating or dehydration
• Stupor or coma
• Recent dramatic weight loss

Complications of thyroid storm include stroke and heart attack, which can lead to death.

Physicians have developed a scoring system that helps them quickly assess symptoms and make a presumptive diagnosis of thyroid storm, so they can rapidly begin treatment. The system involves measuring temperature, heart rate, gastrointestinal symptoms, neurological symptoms, and noting whether the patient has had a previous thyroid storm.

Sometimes, blood tests are done to look for high levels of thyroid hormones; a TSH (thyroid stimulating hormone) test may also be done. Because thyroid storm is a medical emergency, however, there is rarely time to wait for test results and treatment is started immediately.

When treating thyroid storm, doctors often use the "five Bs":

• Block the synthesis of thyroid hormone using antithyroid drugs: This is typically done right away with larger initial loading doses and frequent administration of additional doses. In patients who can't tolerate antithyroid drugs, lithium is sometimes used.
• Block the release of thyroid hormone using a potassium iodide preparation: This is usually given after the antithyroid drugs and helps suppress thyroid hormone release.  
• Block T4 to T3 conversion using a corticosteroid drug, such as hydrocortisone 
• Use of a beta-blocker drug, such as propranolol, to reduce blood pressure and heart rate
• Reduce the reabsorption of thyroid hormones with a bile acid sequestrate such as cholestyramine

Supportive treatment may also include cooling to help reduce body temperature, fluids to combat dehydration, and treatment of any other infections.

Typically, if the treatments are going to work, the improvement will be seen within 24 to 72 hours. 

When thyroid storm does not respond to these approaches, plasmapheresis, a blood filtering treatment, is sometimes done to remove thyroid hormone from the bloodstream. Only a small percentage of the hormone can be removed during each session, so it needs to be performed several times. 

In rare cases, the thyroid is surgically removed, but physicians have to be particularly careful, as the surgery can precipitate a worsening of thyroid storm if hormone levels are already high.

While thyroid storm is rare, it is life-threatening. Always stay up to date on annual physical exams; your doctor will palpate your thyroid to check if it's enlarged (a sign of hyperthyroidism) and test levels of thyroid hormones in your blood as part of a routine check-up. If you have been diagnosed with Graves' disease or hyperthyroidism, always take your medication and have your thyroid levels tested regularly according to your doctor's instructions.