Introduction

A thyroid storm, also referred to as a thyrotoxic crisis, is a rare but potentially life-threatening manifestation of hyperthyroidism or thyrotoxicosis (extreme overproduction of thyroid hormones). This condition is characterised by abnormally high levels of circulating thyroid hormones, thyroxine (T4) and triiodothyronine (T3), often observed in people with untreated or poorly managed hyperthyroidism, such as those with Graves’ disease, toxic multinodular goitre, and toxic thyroid adenoma. 

A triggering factor to a thyroid storm is always required, and they vary. Appropriate treatment of a thyroid storm requires an accurate and prompt diagnosis. Admission to an intensive care unit (ICU) can be required, with cardiac monitoring and ventilatory support if left untreated. Treatment typically involves supportive measures, such as intravenous (IV) fluids, oxygen, cooling blankets, and a combination of medications that address different aspects of the condition, including beta-blockers, antithyroid drugs, iodine, and corticosteroids.^1,2,3

Overview of treatment goals

Management of a thyroid storm requires a multimodal approach to:

• Control the effects of adrenaline on your heart and metabolism: beta-blockers
• Reduce further thyroid hormone production: antithyroid drugs
• Block the release of thyroid hormones: iodine
• Reduce systemic inflammation: corticosteroids

Beta-blockers

Beta-blockers are a class of medications used to manage the hyperadrenergic state associated with a thyroid storm. Excess circulating thyroid hormones have been linked with an increase in the body’s sensitivity to adrenaline, leading to complications, such as tachycardia (abnormally fast heart rate), hypermetabolism (unusually high metabolic rate), and hypertension (high blood pressure). Beta-blockers exert their therapeutic effects by blocking the effects of adrenaline on the heart, blood vessels, and other tissues.^1,2,4

Propranolol is the most widely used beta-blocker for the treatment of a thyroid storm, due to its dual therapeutic effects. Propranolol works by slowing your heart rate and preventing the conversion of the thyroid hormone T4 into T3, the more active form of the hormone. Propranolol is the preferred agent for people assigned female at birth (AFAB) who are nursing and/or pregnant.^2,5

Esmolol is another beta-blocker that is typically used to treat you if you are critically ill and rapid administration is essential. Esmolol has a shorter half-life (~9 minutes) than propranolol (2-4 hours), meaning the effects take place quickly in patients and can be implemented to control your heart rate strictly. Esmolol is generally preferred if you are at risk of developing bronchospasms (constriction of the small airways).⁶

Beta-blockers are important in treating a thyroid storm, but they should be used with caution if you have any of the following: heart failure, asthma, or hypotension (low blood pressure), as they can worsen breathing difficulties.⁴

Antithyroid drugs (thionamides)

Antithyroid drugs play a key role in the treatment of a thyroid storm as they prevent your thyroid gland from producing more hormones. The two most commonly used are propylthiouracil (PTU) and methimazole.

PTU is often the preferred treatment option as it has a dual mechanism of action. Like propranolol, PTU prevents the conversion of T4 to T3. Additionally, it blocks the enzyme responsible for producing new thyroid hormones. Although it is the preferred antithyroid drug, PTU has a higher risk of hepatotoxicity (liver damage) and agranulocytosis (decrease in white blood cell count), and should be avoided if you have a pre-existing liver condition such as cirrhosis.^2,3,7

Methimazole is a more potent inhibitor of thyroid hormone production and is usually preferred for long-term management of hyperthyroidism due to its lower hepatotoxicity risk. However, methimazole is a teratogenic drug, meaning it should be avoided if you are pregnant, especially within the first trimester.^2,3

Iodine therapy

Under normal conditions, iodine is necessary for thyroid hormone production, however, when administered in excessive amounts, iodine can temporarily block the release of thyroid hormones.^2,3

Lugol’s solution (potassium iodide) is typically administered to you at least 1 hour after you have received an antithyroid medication. This is to ensure that your thyroid gland does not use the iodine to produce more hormones. If iodine is given before an antithyroid drug, it can inadvertently cause an increase in thyroid hormone production via a phenomenon called Jod-Basedow (iodine-induced hyperthyroidism).^2,8

Corticosteroids

Corticosteroids are used to treat multiple symptoms of a thyroid storm. They reduce inflammation, help to stabilise your blood pressure, and prevent you from developing adrenal insufficiency. It is when your adrenal glands do not produce adequate levels of essential hormones, which can arise when your body is in a state of high metabolic demand, such as a thyroid storm. Additionally, they help to decrease the conversion of T4 to T3.^1,2,8

Dexamethasone and hydrocortisone are the two most commonly used corticosteroids, of which the former is preferentially used due to its longer half-life and more potent anti-inflammatory effects.^1,2

Supportive therapies

Beyond the use of a combination of medications, additional supportive measures are important in managing thyroid storm symptoms:⁸

• Due to the effects of adrenaline, you may sweat excessively. Therefore, your fluid and electrolyte levels should be closely monitored to prevent dehydration and organ dysfunction (where the organ does not perform its expected function). IV fluids are commonly administered to help maintain your fluid levels
• A cooling blanket may be used to counteract the excess heat production arising from adrenaline-induced hypermetabolism and to make you more comfortable whilst you receive treatment
• You may be given paracetamol (acetaminophen) to control fever arising from hyperthermia
• In severe cases, sedatives may be given to you if you are agitated or in distress
• Oxygen therapy may be administered if you are experiencing respiratory distress

FAQs

What are the signs of a thyroid storm?

Symptoms of a thyroid storm include:

• Tachycardia (abnormally rapid heartbeat) 
• High temperature (104-106 degrees Fahrenheit is common)
• Hypertension
• Sweating
• Nausea and vomiting
• Unexplained weight loss
• Abdominal pain
• Muscle weakness
• Tremor
• Yellowing of the skin and eyes (jaundice)
• Severe agitation and confusion, including psychosis
• Atrial fibrillation (abnormal heart rhythm)
• Loss of consciousness

What is the cause of a thyroid storm?

A thyroid storm can be triggered by several ailments. Although it is more common in people with an existing thyroid condition, certain events, situations and triggers can lead to the sudden even of illness, such as:

• Infection
• Surgery (thyroid or non-thyroid)
• Cardiovascular events (e.g. heart failure)
• Delayed treatment
• Radioiodine therapy
• Abrupt discontinuation of anti-thyroid medication
• Labour (childbirth)

Is a thyroid storm fatal?

A thyroid storm is a medical emergency that can be fatal if you do not seek treatment. The cause of death may be due to another reason, like arrhythmias (abnormal heartbeat), heart failure, hyperthermia, shock, or multiple organ failure. Nonetheless, with prompt diagnosis and treatment, you should see an improvement within 24-72 hours.

What happens if a thyroid storm is not treated?

If you believe yourself or another person to be suffering from a thyroid storm, you should seek immediate medical attention. Untreated, a thyroid storm can lead to the following complications:

• Seizures
• Delirium
• Coma
• Heart failure
• Atrial fibrillation

How long does it take me to recover from a thyroid storm?

With prompt treatment, you should begin to improve within 24-72 hours, although full recovery may take a few weeks, depending on the underlying cause. It is advised that you speak with your medical provider about whether long-term management of underlying hyperthyroidism is necessary.

Can I get a thyroid storm again?

Yes, it is possible to experience a thyroid storm more than once. This may arise if the underlying cause is not addressed or if any of the triggers occur again. 

Is a thyroid storm hereditary?

No, a thyroid storm itself is not a hereditary condition. However, some people may have a genetic predisposition to hyperthyroidism, i.e. an increased chance of developing a particular disease due to specific genetic variations, which can trigger a thyroid storm if untreated or poorly managed.

How can I prevent a thyroid storm?

Preventing a thyroid storm is not always possible due to the many reasons known to trigger it. However, if you have hyperthyroidism, there are steps you can take to lower the risk of you experiencing a thyroid storm, including:

• Ensuring you take your anti-thyroid medication 
• Speaking with your medical provider regularly to ensure your medication is working as it should be

Summary

A thyroid storm, also known as a thyrotoxic crisis, is a serious condition caused by an extreme overproduction of thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3). It mainly affects individuals with untreated or poorly managed hyperthyroidism, such as those with Graves’ disease and toxic multinodular goitre. A triggering factor is always necessary for a thyroid storm, and prompt diagnosis and treatment are essential. Treatment often requires ICU admission and includes supportive care like IV fluids, oxygen, cooling blankets, and medications such as beta-blockers, antithyroid drugs, iodine, and corticosteroids. The treatment goals for managing a thyroid storm involve multiple strategies. Beta-blockers are used to control the effects of adrenaline on the heart and metabolism, while antithyroid drugs help reduce the production of thyroid hormones. Iodine blocks the release of these hormones, and corticosteroids aim to lower systemic inflammation. Additional supportive therapies include monitoring fluid and electrolyte levels, using cooling blankets and paracetamol for fever, administering sedatives if needed, and providing oxygen therapy for respiratory issues.