Content overview

Thyroid storm

Myxoedema coma

Agranulocytosis

Am I at risk?

Most thyroid conditions develop gradually. As thyroid levels go out of range, symptoms tend to creep up on us.

In most people, these symptoms will improve once thyroid levels are corrected with treatment, though this can sometimes take a while.

Very rarely, however, symptoms can develop quickly. This can happen when thyroid conditions are undiagnosed or poorly controlled over a long period. There can also be other causes, such as acute illness, surgery and pregnancy. This can lead to you becoming very unwell and requiring emergency medical treatment. The good news is that with appropriate treatment and monitoring most of these conditions can be prevented.

To help you recognise potential symptoms and triggers and receive urgent medical care, here we look at these ‘thyroid emergencies.’

Thyroid storm

Thyroid storm is a very rare, serious and potentially life threatening complication of hyperthyroidism. This occurs when thyroid hormone levels increase suddenly and cause a rapid flare-up of symptoms. These symptoms are more severe than in hyperthyroidism and usually affect multiple organ systems.

What are the symptoms?

Symptoms can vary from person to person, but common ones include:
• High fever
• Very rapid heart rate, which is often irregular
• Liver dysfunction – yellowing of skin and eyes (jaundice)
• Severe confusion and agitation
• Loss of consciousness

Who is at risk?

People with hyperthyroidism caused by Graves’ disease or toxic thyroid nodules are at risk. Because hyperthyroidism affects more women than men, they are more likely to experience thyroid storm. It is estimated to affect fewer than 1 person in every 100,000 per year and is more common in people over the age of 40.

What are the triggers?

• Undiagnosed or poorly controlled hyperthyroidism i.e. not taking antithyroid drugs consistently or stopping them abruptly
• Infection, such as pneumonia
• Acute illness, such as a heart attack, stroke or diabetic ketoacidosis
• Thyroid surgery, or non-thyroid surgery, when thyroid levels are not well controlled in someone with hyperthyroidism
• Following radioiodine therapy or after having iodinated contrast agent for a CT scan
• Some immunotherapy drugs

How is it treated?

You should be treated in a high dependency care unit or in an intensive care unit. Treatment will usually involve antithyroid drugs, potassium iodide and beta blockers. Intravenous fluids are often required to replace lost fluid.

Other drugs may also be necessary to help control thyroid levels. Doctors will also aggressively treat any known underlying cause, such as an infection.

What can be done to prevent it?

The most effective way of preventing thyroid storm is by managing antithyroid drugs well in people with hyperthyroidism. This includes ensuring antithyroid drugs are not stopped suddenly and that your thyroid levels  are back in reference range (euthyroid) before having elective surgery or labour.

How long will it take to feel better?

Early intervention is crucial as it can be fatal. With the correct treatment, however, most people with thyroid  storm see a marked improvement within 24–72 hours although it could take longer to treat the underlying  cause.

The outlook is worse if:
• You are older
• Have neurological issues when you are admitted to hospital
• Your doctors are unable to treat you with antithyroid drugs and beta blockers due to other health conditions
• You require dialysis and/or a ventilator due to your thyroid storm

What should you do if you are concerned?

A thyroid storm is a medical emergency and can be fatal if left untreated. If you are concerned that you or someone around you may be experiencing it, phone 999 and ask for an ambulance.

Myxoedema coma

When hypothyroidism is left untreated or is very poorly controlled over a long period, it can result in very low  thyroid hormone levels. This severe form of hypothyroidism is called myxoedema. Extremely rarely, this can become so severe that you develop a life-threatening condition called myxoedema coma. Despite its name, most people do not go into a coma, however.

What are the symptoms?

In addition to symptoms associated with severe hypothyroidism (myxoedema), such as facial swelling, skin thickening, and extreme fatigue, with myxoedema coma you may experience:

• Hypothermia
• Shock
• Altered mental state i.e. confusion or mental slowness
• Decreased breathing
• Low blood oxygen levels
• Seizures
• Coma

Who is at risk?

Myxoedema coma is a complication of severe hypothyroidism. It is more common in older people who have this  hypothyroidism. It is extremely rare, estimated to affect around 1 in a million people. It typically affects females, often over the winter months.

What are the triggers?

This condition mostly affects people with poorly controlled hypothyroidism, either autoimmune or following definitive treatment for hyperthyroidism. Often there is an additional trigger which can include:
• Sudden, acute illness such as a cardiac event or stroke
• Infection
• Gastrointestinal bleed
• Trauma
• Winter months
• Certain drugs, e.g. tranquilisers and diuretics

How is it treated?

Early intervention is vital in this condition as it can be fatal. You should be treated in a high dependency care unit or an intensive care unit. You will be given intravenous* (IV) steroids followed by replacement thyroxine  intravenously. If you fail to improve, you may also be given L-T3 (liothyronine) intravenously. Once you start to improve, you will be taken off IV medication and usually be given your medication orally. You will also be given  aggressive treatment for any other causes that may have triggered the myxoedema coma. The outlook is poorer in older people.

What can be done to prevent it?

Ensuring you take your thyroid medication as prescribed and having your thyroid function monitored regularly is the best way to prevent this condition. Thyroid function tests are usually done once a year in people with  hypothyroidism or more frequently if your thyroid results have been abnormal, after a change of dose or if you  are feeling unwell.

What should you do if you are concerned?

Myxoedema coma is a medical emergency that requires immediate medical attention by phoning 999 and asking for an ambulance.

Agranulocytosis

Like most drugs, antithyroid drugs (carbimazole and propylthiouracil) can have side effects. While most of these are minor, the most serious potential side effect of both drugs is bone marrow depression. This can lead to a potentially life-threatening condition called agranulocytosis. 

In this condition, the white blood cells are lowered, making it harder for your body to fight infection. 

What are the symptoms?

• Sore throat
• Mouth ulcers
• Fever

Who is at risk?

This is an extremely rare condition thought to affect less than 1 in 500 people taking antithyroid drugs, though it  is possibly as low as 1 in 3,000. The risk of agranulocytosis is less when taking lower doses. Where it occurs, it is usually during the first three months of antithyroid drug treatment, but it can also rarely happen much later  than this.

How is it treated?

If you, or your doctor, are concerned that you have symptoms, you should stop taking your antithyroid drugs immediately. You should not take another dose of them until you know that your white blood cell count is  normal.

How long will it take to feel better?

Your neutrophil count should return to normal 1 to 3 weeks after stopping your antithyroid drugs, if this has  been confirmed as the cause of the issue.

What should you do if you are concerned?

If you develop any of the symptoms described, you should stop taking your antithyroid drugs immediately and  go to your GP or nearest Emergency Department and ask them to do a full blood count, which includes a white  cell count. You should tell the medical team about the medication you are taking. Do not take another dose of your antithyroid drugs until your doctor has said it is ok for you to do so.

Although sore throats and mouth ulcers are common, and your blood test may well come back normal, it is  better to err on the side of caution.

Am I at risk?

Although it is important to know about these conditions, and what to do if you are worried about symptoms,  they are thankfully extremely rare. As we have outlined, your risk can be greatly reduced by taking your thyroid medication as prescribed, having regular thyroid function tests and seeing a doctor promptly if something does not feel right.

Further reading

Our antithyroid drugs alert card is a handy reminder of rare side effects to look out for and what to do if symptoms develop.

Download or order your free alert card

*Given directly into a vein via a needle or tube.