Introduction

Thyroid storm, also known as thyrotoxic crisis, is a life-threatening condition associated with untreated or under-treated hyperthyroidism.¹ Today, given advancements in identifying and appropriately managing hyperthyroidism, the development of thyroid storm is rare. However, in those who do develop it, mortality rates remain high, at an estimated 8-25%. 

Thyroid storm is a medical emergency, and several factors influence the prognosis and recovery of those who develop the condition. Without quick recognition and the timely and aggressive treatment of patients in intensive and high-dependency medical units, it can result in death, from heart failure and heart attack, or multiple organ failure.²

Background

What is the thyroid gland?

The thyroid gland is a hormone-producing organ located at the front of the neck, under the voice box. It plays an important role in the way our body uses energy for functions such as growth, development and metabolism. In healthy individuals, the thyroid gland releases a continuous, steady amount of thyroid hormones, triiodothyronine (T3) and thyroxine (T4), and calcitonin into the bloodstream. The release of these hormones from the thyroid gland is controlled by hormonal interactions between the hypothalamus, anterior pituitary and thyroid gland. 

In certain situations where more energy is required by the body, such as illness, growth or pregnancy, the thyroid gland can increase hormone production to meet the increased needs.³ 

What do thyroid hormones do?

Thyroid hormones T3 and T4 control the amount of energy our body needs while at rest. An increase in these hormones increases our basal metabolic rate and makes the cells of our body work harder. As a result, it can affect the body through:

• Increase in body temperature
• Increase in heart rate
• Increase in food metabolism
• Growth in children⁴ 

What is thyroid storm?

Hyperthyroidism

An overactive thyroid, also called hyperthyroidism, is a condition where the thyroid gland is producing too many hormones than the body requires. There are several causes for increased thyroid hormone activity:

• Graves’ disease (most common cause)
• Overactive thyroid nodules
• Thyroiditis, inflammation of the thyroid gland
• Excess iodine intake 
• Overuse of thyroid hormone medicines
• Tumours of the pituitary gland

Thyrotoxicosis is the clinical syndrome that results from hyperthyroidism, where the body has been exposed to too high levels of circulating thyroid hormones, resulting in many functions of the body speeding up. This can lead to symptoms such as weight loss, fast, irregular heartbeat, sweating, frequent bowel movements, and high blood pressure.⁵

Thyroid storm

Thyroid storm is an extreme, abrupt, life-threatening complication that occurs in individuals within the spectrum of thyrotoxicosis. These individuals usually have an underlying cause of excess thyroid hormone activity, and a second trigger to cause this exacerbation. Triggers can include:

• Abrupt stopping of antithyroid medication
• Sepsis or acute infections
• Surgery (thyroid and non-thyroid)
• Iodine therapy
• Drugs
• Diabetic ketoacidosis 
• Pregnancy⁶ 

During thyroid storm, an individual can clinically present with classic features of fever, high heart rate, nausea, vomiting and diarrhoea, restlessness and agitation, dehydration and delirium or coma.⁷

Diagnosis 

Thyroid storm diagnosis is made on clinical signs and symptoms for people with pre-existing hyperthyroidism, rather than laboratory findings. 

There are two different systems used to assess the probability and severity of thyroid storm:

• The Burch-Wartofsky Point Scale (BWPS) is a scoring scale, giving a numerical value of likelihood and severity of thyroid storm
• The Japanese Thyroid Association (JTA) scoring system quantitatively determines the probability of thyroid storm.

Both systems use the presence of central physical symptoms of thyrotoxicosis to assess the likelihood of thyroid storm, based on the severity of these symptoms. Classic features include:

• High temperature 
• High heart rate
• Gastrointestinal tract symptoms, such as diarrhoea, pain, nausea and vomiting
• Dehydration
• Central nervous system disturbances, such as restlessness, extreme agitation, delirium, seizure and coma
• Signs and symptoms of organ failure, such as heart failure, may be present^5,8

These scales are used as guidelines for diagnosis, and with no unique laboratory findings, such as tests in blood or urine samples, which can help the official diagnosis, clinical judgment remains largely critical in the official diagnosis.⁷

Mortality rates of thyroid storm

Mortality rates

Historically, thyroid storm was nearly always fatal. Death from thyroid storm is not as common given advances in early diagnosis and aggressive treatment in the intensive care unit, which have improved mortality rates to 8-25%. Improved management of hyperthyroidism has also made the development of thyroid storm a rare condition.

While mortality rates have improved, it still remains one of the most life-threatening hormone-related emergencies, and recovery is dependent on several factors which influence it. Thyroid storm needs to be medically managed promptly, as without treatment, the mortality rate remains high at 80-100%.⁸ 

Death can be a result of organ failures, including cardiac, liver, brain, or body shock, and hyperthermia. Additionally, some patients who do survive suffer from long-term irreversible effects, including brain damage, kidney damage, and psychosis.⁷

Factors influencing recovery

Age and sex variations

The risk of development and mortality rates of thyroid storm vary by sex. Given that certain risk factors for developing thyroid storm are more common in people assigned female at birth (AFAB), it is more frequently seen in people AFAB than in people assigned male at birth (AMAB). However, in those who develop, the risk of mortality is higher among people AMAB. 

Mortality increases with age in both genders. The death rate of those less than 60 years old is <1.5% in both genders. However, in people older than 60 years old, the death rate increases. People AFAB death rate in this age group is 10.9%, and people AMAB death rate is even higher at 16.7%. The age group with the highest mortality rate are those >80 years old.^9,10

Severity at presentation

Patients with more severe disease show poorer recovery. These patients score higher on the Burch-Wartofsky Point Scale, as they have more severe symptoms, such as higher fever, severely high and abnormal heart rate, severe central nervous system symptoms, and signs of organ failure. Therefore, those with a higher score show poorer recovery.^8,11,12 

Time and response to treatment

Thyroid storm is a medical emergency; therefore, recognising and seeking medical treatment immediately is critical. Urgent admission to the intensive care unit on diagnosis is usually needed.

Treatment consists of:

1. Supportive measures to manage presenting symptoms of temperature, dehydration, shock - these include intravenous fluids, oxygen, temperature control through cooling blankets/paracetamol
2. Specific therapy to reduce production and release of thyroid hormones and their effects – antithyroid drugs, drugs to reduce heart rate (beta-blocking agents), steroids
3. Treatment of a specific trigger identified, such as an infection

The chances of survival increase the quicker someone seeks and receives medical care, with most patients feeling much better within 24 hours of therapy. If, in rare cases, medical therapy is ineffective or patients develop side effects, they may need thyroid surgery, which can influence patient recovery.⁷

Existing illnesses and complications

People who have existing illnesses have a higher risk of mortality. Illnesses which increase the risk of death are cardiovascular disease, medically treated diabetes, obesity, dementia and chronic obstructive pulmonary disease.¹³

Summary

Thyroid storm is a life-threatening medical emergency, resulting from untreated or incorrectly treated hyperthyroidism, usually triggered by a superimposed factor. Once an entirely fatal complication, advancements in early recognition and prompt care of people suffering from it have significantly reduced mortality.

While mortality rates have improved, they still vary widely, ranging from 8 to 25%. This is because recovery is influenced by a number of factors, including age, gender, pre-existing illness, severity of clinical symptoms at presentation and the speed at which a patient seeks and receives medical care. Therefore, education on the prevention of the development of thyroid storm and early recognition of signs and symptoms is important in improving the overall prognosis.