Thyroid storm (thyrotoxic crisis): symptoms, causes and emergency treatment

The thyroid is a butterfly-shaped gland in the neck that produces hormones affecting things such as heart rate and body temperature. An overactive thyroid (hyperthyroidism) produces too much of these hormones. The NHS says that rarely, an undiagnosed or poorly controlled overactive thyroid can lead to a serious, life-threatening condition called a thyroid storm, which is a sudden flare-up of symptoms.

A UK clinical reference article describes hyperthyroid crisis, or thyrotoxic storm, as an extreme manifestation of thyrotoxicosis due to overproduction of thyroid hormones. It says early recognition and aggressive treatment are essential, which is why it is handled as an emergency rather than something to monitor at home.

The great majority of people with an overactive thyroid never experience a thyroid storm. The same article says approximately 1 to 2 per cent of patients with hyperthyroidism progress to a hyperthyroid crisis.

The NHS lists the symptoms of a thyroid storm as a rapid heartbeat, a high temperature, high blood pressure, yellowing of the skin and eyes (jaundice), severe agitation and confusion, and loss of consciousness. The clinical reference article describes a sudden onset of severe hyperthyroidism with a very high temperature, dehydration, a very fast heart rate with or without an irregular rhythm, nausea, vomiting, diarrhoea, abdominal pain and jaundice, and with confusion, agitation, delirium, psychosis, seizures or coma.

The picture can be varied and hard to recognise, particularly in a person who has been injured or is already unwell, because many of these signs overlap with other emergencies. For that reason the NHS advice is to treat the possibility seriously and call 999 rather than wait.

• A very fast or irregular heartbeat.

• A high temperature and sweating.

• Severe agitation, confusion or unusual behaviour.

• Vomiting, diarrhoea or abdominal pain.

• Yellowing of the skin and eyes.

• Drowsiness, collapse or loss of consciousness.

The NHS is clear: a thyroid storm is a medical emergency, and if you think you or someone in your care is experiencing it you should call 999 to ask for an ambulance immediately. If you have a known overactive thyroid and develop a high temperature, a racing heart and confusion or agitation, do not wait to see whether it passes.

Tell the ambulance crew and hospital staff that you have an overactive thyroid and which medicines you take, including antithyroid tablets and any recent changes. If you have recently had radioactive iodine, surgery or a serious infection, say so too.

The NHS says a thyroid storm can be triggered by an infection, pregnancy, not taking your medicine correctly and damage to the thyroid gland, such as a punch to the throat. The clinical reference article adds acute illness, recent trauma including surgical stress, heart attack or stroke, diabetic emergencies, labour and delivery, pulmonary embolism, certain drugs and contrast media, radioiodine treatment, overdose of thyroid hormone tablets and thyroid surgery without adequate preparation.

The underlying thyroid condition is most often Graves' disease, according to the article, or a toxic multinodular goitre. The NHS says about 4 in every 5 people with an overactive thyroid have Graves' disease.

Stopping antithyroid medicine suddenly is one preventable trigger. If you cannot take your tablets because of illness, vomiting or side effects, contact your GP or endocrinology team the same day.

The clinical reference article says the diagnosis is clinical: a combination of the presentation and laboratory values confirming hyperthyroidism. It also notes that the degree to which thyroid hormone levels are raised does not determine whether a crisis is present, and that treatment should start as soon as a thyroid crisis is suspected, even before test results are back. Hospital teams look for the trigger, for example by screening for infection, and check heart, kidney, liver and electrolyte status.

The article describes four components of treatment: reducing thyroid hormone production and release with antithyroid medicine, with iodine given afterwards; dealing with the hormones already in the circulation, using beta-blockers to control the heart rate unless they are not suitable, and hydrocortisone; finding and treating the trigger, for example an infection; and supportive care for the body, including fluids, oxygen, cooling and paracetamol. Where these fail, options such as plasmapheresis or, rarely, early thyroidectomy are used. Further thyroid management is under an endocrinologist.

Because the article states that untreated thyroid crisis is usually fatal and that mortality remains significant even with early treatment, the emphasis of UK advice is rapid recognition and emergency hospital care.

The NHS says an overactive thyroid is usually treatable, with antithyroid medicine, radioactive iodine or surgery, and complications such as thyroid storm are more likely if the condition is not treated or well controlled. Taking medicines as prescribed, attending follow-up blood tests and telling doctors about your thyroid condition before surgery or other procedures are the main protective steps.

If you are planning surgery on your thyroid, the clinical reference article notes that inadequate pre-operative preparation is a risk factor, which is one reason surgery is planned with your endocrinology team. If you become pregnant, tell your doctor immediately, as pregnancy is listed by the NHS as a trigger and carries its own risks when an overactive thyroid is not well controlled.

Thyroid storm is treated as an emergency, so care is delivered through ambulance services and hospital emergency departments in the NHS, with intensive care and endocrinology input. This is not something that can be arranged privately in advance or managed at home.

For ongoing thyroid care, a GP or endocrinologist, NHS or private, can review your medicines and blood tests. The British Thyroid Foundation is the charity the NHS directs people with an overactive thyroid to for help and support.