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.
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 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 responds 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 infection such as sepsis
- Induced anesthesia and surgery that causes physical stress on the body
- Severe burns
- Emotional stress
- Stopping antithyroid medication
- Radioactive iodine therapy
- Trauma to the thyroid gland: even a 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, nonsteroidal anti-inflammatory drugs), amiodarone and chemotherapy
- Toxemia of pregnancy
- Heart disease
- Intense physical activity
Symptoms and signs
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.
There are no specific tests exclusive to diagnose a thyroid storm. Diagnosis is arrived at more from the history of hyperthyroidism and 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
- Increased alkaline phosphatase
- ECG to rule out cardiac complications, if any
On any of the 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.
The treatment is aimed at primarily to treat the 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 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 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.
- IV fluids (especially dextrose) and electrolytes to fight dehydration
- Antipyretics 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
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%.