Synopsis
Recognise decompensated severe hypothyroidism before coma is established, deliver endocrine-critical-care treatment in the correct sequence, and correct precipitating and metabolic threats safely.
- The syndrome is severe physiological decompensation from hypothyroidism and does not require literal coma; altered cognition may range from slowing and delirium to unresponsiveness.
- Think of the cluster: hypothermia, bradycardia, hypotension, hypoventilation or hypercapnia, hyponatraemia, hypoglycaemia, oedematous appearance and reduced consciousness.
- Infection, cold exposure, myocardial infarction, stroke, sedatives or opioids, surgery and interruption of levothyroxine are important precipitants.
- Obtain thyroid tests and cortisol promptly, but treatment must not be delayed for confirmatory results when the clinical syndrome is convincing.
- Give parenteral hydrocortisone before thyroid hormone until clinically important adrenal insufficiency is excluded, because replacement can precipitate cortisol collapse.
- After parenteral hydrocortisone, the current levothyroxine injection SmPC recommends an adult intravenous loading dose of 200–500 micrograms, never above 500 micrograms, followed by 1.2 micrograms/kg daily, usually 75–90 micrograms; use the lower end or a modified plan when cardiac risk is high.
- Provide ventilatory support early when respiratory drive is inadequate; normal oxygen saturation does not exclude dangerous carbon-dioxide retention.
- Warm passively and gradually, correct sodium and glucose cautiously, treat infection empirically when suspected, and avoid rapid shifts that add neurological or circulatory injury.
- Continuous cardiac, temperature, fluid and biochemical monitoring is essential because arrhythmia, ischaemia and treatment-related instability can emerge during recovery.
Key red flags
Lethargy, slowed responses, confusion, psychosis, seizures, stupor or coma may occur. A fall in consciousness alongside hypothermia or bradycardia is particularly concerning and mandates airway assessment.
Slow shallow breathing, upper-airway oedema, obesity, effusions or reduced respiratory drive can produce hypoxia and hypercapnia. Obtain a blood gas and involve anaesthesia early when ventilation is failing.
Bradycardia, low cardiac output, hypotension, conduction delay, pericardial effusion and occasionally heart failure or ischaemia create a fragile circulation that can be worsened by aggressive warming or hormone loading.
Hyponatraemia, hypoglycaemia, raised creatine kinase, renal impairment and respiratory acidosis support severe systemic disease but are not specific; correction speed and underlying mechanism must be assessed.
Pneumonia or urinary infection may lack fever in a hypothermic patient; review myocardial ischaemia, stroke, trauma, drug exposure and omitted hormone even if one trigger initially seems obvious.
Investigation priorities
Identify immediate ventilatory, circulatory and thermoregulatory failure.
Management branches
Severe hypothyroid decompensation is clinically suspected.
- Call critical care, endocrinology and senior acute support; perform ABCDE with continuous ECG, core temperature, glucose and urine-output monitoring.
- Secure oxygenation and ventilation, obtain blood gas and prepare intubation when consciousness or carbon-dioxide clearance is inadequate.
- Take thyroid tests, cortisol, cultures and metabolic bloods rapidly, but begin steroid, supportive and infection treatment without waiting for results.