Thyroid Storm

Written by Kristeen Moore
Medically Reviewed by George Krucik, MD

What Is Thyroid Storm?

Thyroid storm is a life-threatening health condition that is associated with untreated or undertreated hyperthyroidism. During thyroid storm, an individual’s heart rate, blood pressure, and body temperature can soar to dangerously high levels. Without prompt, aggressive treatment, thyroid storm is often fatal.

The thyroid is a small, butterfly-shaped gland located in the middle of your lower neck. It produces two hormones (triiodothyronine (T3) and thyroxine (T4)) that control the rate at which every cell in your body works (your metabolism). If you have hyperthyroidism, your thyroid is producing too much of the two hormones. This causes all your cells to work too quickly. For example, your respiration rate and heart rate will be higher than they normally would. You may even speak far more quickly than you usually do.

Causes of Thyroid Storm

Thyroid storm is rare. Only one to two percent of people with hyperthyroidism will develop thyroid storm. It develops in people who have hyperthyroidism but are not receiving appropriate treatment. This condition is marked by the extreme overproduction of the two hormones produced by the thyroid gland. Not all people with hyperthyroidism will develop thyroid storm. According to the National Library of Medicine, the most common causes of this condition include:

  • severe undertreated hyperthyroidism
  • untreated overactive thyroid gland
  • infection associated with hyperthyroidism

Individuals with hyperthyroidism may develop thyroid storm after experiencing trauma, surgery, severe emotional distress, stroke, diabetic ketoacidosis, congestive heart failure, or pulmonary embolism.


Symptoms of thyroid storm are similar to those of hyperthyroidism, but they are more sudden, severe and extreme. The symptoms are often debilitating, which is why people with thyroid storm might not be able to seek care on their own. Common symptoms include:

  • racing heart rate (tachycardia) that exceeds 140 beats per minute and atrial fibrillation
  • high fever
  • persistent sweating
  • shaking
  • agitation
  • restlessness
  • confusion
  • diarrhea
  • unconsciousness

Diagnosing Thyroid Storm

Individuals with hyperthyroidism who experience any symptoms of thyroid storm are typically admitted to the emergency room. If you suspect you or someone else has thyroid storm symptoms, call 911 immediately. People with thyroid storm generally exhibit an increased heart rate, as well as a high top number in blood pressure.

A doctor will measure your thyroid hormone levels through a blood test. Thyroid stimulating hormone (TSH) levels tend to be low in hyperthyroidism and thyroid storm. According to the National Library of Medicine, normal TSH levels range between 0.5 and 3.0 mlU/L. (National Institutes of Health). T3 and T4 hormones are higher than normal in people with thyroid storm.


Thyroid storm develops abruptly and affects all the systems of your body. Treatment will begin as soon as thyroid storm is suspected—usually before lab results are ready. Antithyroid medication like propylthiouracil (also called PTU) or methimazole (Tapazole) will be given to reduce the production of these hormones by the thyroid.

Hyperthyroidism requires ongoing care. People with hyperthyroidism may be treated with radioactive iodine, which destroys the thyroid, or a course of drugs to suppress thyroid function temporarily. Pregnant women who have hyperthyroidism cannot be treated with radioactive iodine because it would harm the unborn child. In those cases, the woman’s thyroid would be removed surgically.

Patients should avoid taking iodine in lieu of medical treatment, as this can worsen the condition.

If your thyroid is destroyed by radioactive iodine treatment or removed surgically, you will need to take synthetic thyroid hormone for the rest of your life.

Long-Term Outlook

Thyroid storm requires immediate, aggressive emergency medical attention. When left untreated, thyroid storm can cause congestive heart failure. Patients may also experience fluid-filled lungs. According to S. Karger, the mortality rate for people with untreated thyroid storm is 75 percent.

The chances of surviving thyroid storm increase if you quickly seek medical care. Related complications may be lessened once your thyroid hormone levels are returned to the normal range (known as euthyroid).

Preventing Thyroid Storm

The most effective way to prevent the onset of thyroid storm is to keep up with your thyroid health plan. Take your medications properly. Keep all appointments with your doctor and follow through with blood work orders as needed.

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