Nursing care
Thyroid storm vs myxoedema coma: two mirror-image emergencies
Written and reviewed by Elena Vasquez, BSN, RN, CMSRN · 4 min read · Updated October 2026
Short answer
They are mirror images. Thyroid storm is a hypermetabolic emergency with high fever, a fast heart rate, and agitation or delirium. Myxoedema coma is a hypometabolic emergency with low body temperature, a slow heart rate, slowed breathing and falling consciousness. Temperature and heart rate separate them fastest. Both are life threatening and often follow infection, surgery or trauma.
The deciding contrast: temperature and heart rate
In thyroid storm, excess thyroid hormone drives metabolism hard. MSD Manuals lists fever, marked restlessness, emotional instability, confusion and tachycardia that can progress to cardiovascular collapse, with nausea, vomiting and diarrhoea. The patient is hot, fast and agitated, and may become psychotic or comatose.
In myxoedema coma, severe untreated hypothyroidism slows everything down. MSD Manuals describes coma with extreme hypothermia, absent reflexes, seizures and respiratory depression with carbon dioxide retention. Bradycardia and low blood pressure are part of the usual teaching picture, so the patient is cold, slow and drowsy. Standard thermometers may miss how low the temperature is.
Shared features that do not separate them
Both are uncommon emergencies in people with known or unrecognised thyroid disease, and both are often triggered by infection, trauma, surgery or other acute illness. Altered mental status occurs in both, ranging from confusion to coma, so a change in consciousness alone does not tell you which one is present.
Thyroid blood tests confirm the underlying disorder but take time, and treatment usually starts on clinical grounds. Severe illness of either kind can end in cardiovascular collapse. The vital sign trend, the history of thyroid disease and the medication list give the nurse the most useful early clues.
Nursing priorities in thyroid storm
Airway, breathing and circulation come first, with continuous cardiac monitoring because of tachycardia and arrhythmia risk. The nurse gives ordered medicines promptly: a beta blocker for heart rate, a thionamide such as propylthiouracil, and iodine only after the thionamide, as MSD Manuals advises. Corticosteroids are commonly ordered as well.
Cool the patient with cooling blankets as ordered, give intravenous fluids and glucose as prescribed, and keep the environment calm and quiet. Monitor temperature, heart rhythm, fluid balance and mental state closely. Nursing texts commonly advise avoiding aspirin for the fever because it may raise free hormone levels; follow local protocol.
Nursing priorities in myxoedema coma
Breathing is often the immediate threat, because hypoventilation and carbon dioxide retention can progress to respiratory failure. Assess airway and respiratory effort, prepare for possible mechanical ventilation, and give intravenous thyroid hormone as ordered. Glucocorticoids are usually given too, because adrenal insufficiency may coexist.
Rewarm gradually with blankets rather than aggressively, because MSD Manuals warns that rapid rewarming can trigger hypotension or arrhythmias. Fluids need care, since hypothyroid patients excrete water poorly, so watch sodium and fluid balance. Sedatives and opioids are given cautiously, if at all, because slowed metabolism and depressed breathing make them dangerous.
Hypothetical practice scenario
Hypothetical scenario, not a real exam item: an older client with untreated hypothyroidism is found drowsy after a cold night alone. Temperature is low, heart rate is slow and respirations are shallow. Which action comes first: apply a heated warming device on its highest setting, assess airway and breathing, or give the sleeping tablet the client missed?
Assessing airway and breathing comes first, because hypoventilation is the most immediate threat. Rapid active warming is tempting because the client is cold, but aggressive rewarming can cause hypotension and arrhythmias, so warming should be gradual. A sedative would worsen respiratory depression and should be held and reported.
Sources and further reading
MSD Manual Professional Version: Hyperthyroidism. Thyroid storm triggers and features, propylthiouracil before iodine, beta blocker, corticosteroids, cooling and intravenous dextrose and fluids.
MSD Manual Professional Version: Hypothyroidism. Myxoedema coma triggers and features, intravenous thyroid hormone, glucocorticoids, ventilation, impaired water excretion and the warning against rapid rewarming.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our endocrine practice questions are the closest set to what this page covers.
Common questions
Why is iodine given after the antithyroid drug in thyroid storm?
The thionamide blocks new hormone production. MSD Manuals advises giving propylthiouracil before iodine, because iodine given first can worsen thyroid hormone release. If both are ordered together, the nurse confirms the sequence and timing with the prescriber.
Can thyroid storm and myxoedema coma both cause confusion?
Yes. Thyroid storm tends to cause agitation, restlessness, delirium or psychosis, while myxoedema coma causes slowing, drowsiness and stupor. Both can end in coma, so the vital sign pattern is more useful than mental status alone.
What triggers each emergency?
Thyroid storm is often triggered by infection, trauma, surgery, embolism, diabetic ketoacidosis or preeclampsia in someone with poorly controlled hyperthyroidism. Myxoedema coma follows illness, infection, trauma, cold exposure or central nervous system depressant medicines in someone with severe hypothyroidism.