What is a thyroid storm? Definition

Thyroid storm also referred to as thyrotoxic crisis, is a rare but acute condition caused by a very high increased rate of thyroid hormones due to a hyperactive thyroid. It is the most advanced case of thyrotoxicosis and if left untreated, it is invariably fatal. Early diagnosis and prompt treatment, therefore, are crucial for recovery.

It is a rare but life-threatening complication of Graves’ disease and is also referred to as accelerated hyperthyroidism or thyrotoxic crisis.

The body is in a continuous state of hypermetabolic state due to the high levels of thyroid hormones, free triiodothyronine (T3) and free thyroxine (T4) in the blood induced by excessive secretion of TSH from the pituitary gland.

A hypermetabolic state is a condition in which the body’s basal metabolic rate is abnormally high. This can have a detrimental effect on the body.

Clinically, thyroid storm presents with fever, tachycardia, hypertension, and neurological and gastrointestinal abnormalities. And, it can be diagnosed with these presenting clinical signs and symptoms. There are no specific lab tests to diagnose this condition.

About 1% to 2% of people with hyperthyroidism will develop thyroid storm, which is a fairly low incidence. But, the mortality rate in these cases is as high as 50% to 90%.

With early treatment, the mortality rate drops to less than 20%. In essence, it means that it is very likely that a thyroid storm will kill you if you do not take proper treatment.


The real reason behind the parthenogenesis of a thyroid storm is still not established. Of course, the high accompanying levels of free thyroid hormones should explain this phenomenon, but such values are seen even in uncomplicated cases of hyperthyroidism.

And, a storm has occurred even in cases with normal total thyroid hormone levels. This indicates that there is something more to it, that gives rise to a storm.

It is possible that the thyroid storm can be triggered not by high thyroid hormones but by the altered way in which the body tissues respond to those hormones.

Though nothing definite is confirmed, there are certain suggestions. Accompanying adrenergic hyperactivity or an altered interaction between thyroid hormones and catecholamines are some forthcoming suggestions. However, blood levels of adrenaline and noradrenaline are not increased during thyroid storm.

Causes and triggers

Those people with thyrotoxicosis who do not take treatment for their hyperthyroidism or those who have been improperly treated are more at risk. In people with thyrotoxicosis, the following factors can trigger a thyroid storm:

  • Severe infections such as sepsis
  • Induced anesthesia and surgery that causes physical stress on the body
  • Severe burns
  • Emotional stress
  • Stopping thyroid medication
  • Radioactive iodine therapy
  • Trauma to the thyroid gland: even vigorous palpation of the gland can trigger a thyroid storm
  • Diabetic ketoacidosis – a potentially life-threatening complication of diabetes mellitus
  • Certain anticholinergic and adrenergic drugs (such as pseudoephedrine, salicylates, and nonsteroidal anti-inflammatory drugs), amiodarone, and chemotherapy
  • Toxemia of pregnancy
  • Stroke
  • Heart disease
  • Intense physical activity
  • Very rarely, thyroid storm can develop in a patient with hypothyroidism. It can develop in patients with hypothyroidism on levothyroxine due to regular high doses of hypothyroid medication.

Symptoms and signs of thyroid storm

Thyroid storm symptoms typically have an acute and sudden onset. You suddenly start to feel different due to their onset. They include symptoms that present due to hyperthyroidism and some more accompanying features.

Symptoms that present due to hyperthyroidism include a rapid heart rate often above 140 beats per minute, restlessness, and agitation.

Other features include a very high fever (usually above 104F), excessive sweating, high blood pressure, altered mental state, shaking, vomiting, and diarrhea. The patient may go into heart failure and even become unconscious.

Physical signs of thyroid storm, include:

  • Goiter, which is an enlargement of your thyroid gland.
  • Ophthalmopathy, which is a complication of Graves’ disease that involves eye tissues such as swelling and bulging eyes.
  • Lid lag
  • Hand tremors.
  • Warm and moist skin.
  • Tachycardia or atrial fibrillation.

Diagnostic criteria

There are no specific tests to diagnose a thyroid storm. Diagnosis is arrived at more from the history of hyperthyroidism and taking of improper treatment.

Symptoms and the accompanying signs described above play an important role to the physician in confirming the diagnosis of thyroid storm.

On testing, TSH levels will be low and the free T3 and T4 levels will be elevated. Total T3 and T4 may be normal.

Other lab findings that may present include:

  • Elevated WBC count
  • High blood sugar levels (hyperglycemia)
  • Elevated aspartate aminotransferase (AST) and bilirubin
  • Hypercalcemia
  • Increased alkaline phosphatase
  • ECG to rule out cardiac complications, if any

Thyroid storm management guidelines

On any of the above-mentioned symptoms presenting themselves (which is usually abrupt), you must visit the doctor for their management. The doctor will usually diagnose the condition from symptoms and signs and start treatment before the confirming lab results come in.

Antithyroid medication

The treatment is aimed at primarily treating hyperthyroidism. He will start with antithyroid medication like propylthiouracil (also called PTU) or methimazole (Tapazole) to slow down the production and release of the thyroid hormones by the thyroid.

Radioactive iodine (RAI)

The doctor may also use radioactive iodine to ablate the thyroid tissue and slow down thyroid hormone production.


Beta-1-selective beta-blockers (e.g. metoprolol) are recommended to protect the end organs from the ill effects of thyroid hormones. Secondly, this medicine also prevents the conversion of T4 to T3. T3 is the active thyroid hormone that can cause damage.


Due to the hypermetabolic state of the body caused by high thyroid hormone levels, cortisol is broken down leading to adrenal insufficiency. Cortisol is a steroid hormone, which regulates metabolism, the body’s immune response, and the capacity to fight stress.

To fight this adverse effect of thyroid storm, intravenous corticosteroids, preferably hydrocortisone and dexamethasone, are given to all patients with thyroid storm. Doses are fixed on a patient-to-patient basis.


Surgery, either subtotal or total thyroidectomy, is another option. Each of the treatment options has its own indications and are described in the post on hyperthyroidism.

For example, antithyroid medication and radioactive iodine are contraindicated during pregnancy and even if you are planning a pregnancy in the next nine months. At such a time, surgery becomes the only option.

If the thyroid gland is ablated with radioactive iodine or removed surgically, the patient will have to take synthetic thyroid hormones throughout his life.

Supportive treatment

  • IV fluids (especially dextrose) and electrolytes are given to fight dehydration
  • Antipyretics are given for fever. Avoid giving aspirin because it decreases protein binding, which leads to elevated free T3 and free T4 levels.
  • Supplemental oxygen, if required
  • Treating cardiac arrhythmias if present
  • Severe agitation can be treated with chlorpromazine

With the proper medical treatment, you’ll most likely respond and feel better within 24 hours. However, it could take up to a week to treat the cause of your thyroid storm.

Long-term prognosis

If left untreated, thyroid storm kills 75 to 90 out of 100 people. Death occurs due to ventricular arrhythmia, congestive cardiac failure, extreme body temperature elevation, multiple organ failure, and some other factors.

Extreme caution is required because even with early diagnosis and treatment, the mortality rate is about 20%.