Signs of Myxedema Coma
Myxedema coma presents with a constellation of critical signs including hypothermia, altered mental status, bradycardia, hypoventilation, hypotension, and hyponatremia, requiring immediate recognition and treatment to prevent mortality. 1
Cardinal Clinical Features
Neurological Signs
- Altered mental status (ranging from confusion to coma)
- Decreased level of consciousness
- Cognitive slowing/intellectual slowness
- Slurred speech
- Seizures (in severe cases)
Vital Sign Abnormalities
- Hypothermia (often profound, <95°F/35°C)
- Bradycardia
- Hypotension
- Hypoventilation/respiratory depression
- Decreased respiratory rate
Metabolic Abnormalities
- Hyponatremia
- Hypoglycemia
- Hypercapnia (elevated CO2)
- Hypoxemia
Physical Examination Findings
- Non-pitting edema (myxedema) of face, hands, and extremities
- Dry, cool skin
- Delayed relaxation phase of deep tendon reflexes
- Macroglossia (enlarged tongue)
- Periorbital puffiness
- Hair loss
- Hoarse voice
Laboratory Findings
- Severely elevated TSH (typically >50 mIU/L)
- Low free T4
- Low free T3
- Elevated CPK
- Elevated liver enzymes
- Elevated lactate dehydrogenase
Precipitating Factors
Myxedema coma is often precipitated by:
- Infections (particularly pneumonia)
- Cold exposure
- Sedatives/anesthetics
- Discontinuation of thyroid medication
- Trauma
- Stroke
- Gastrointestinal bleeding
- Heart failure
Cardiovascular Manifestations
Cardiac involvement is particularly important as it contributes significantly to mortality 2:
- Bradycardia
- Decreased cardiac output
- Pericardial effusion (in some cases)
- ECG changes (low voltage, flattened T waves)
- Dilated cardiomyopathy (in severe cases)
Diagnostic Challenges
Myxedema coma can be misdiagnosed as:
- Sepsis
- Stroke
- Drug overdose
- Primary central nervous system disorder
Clinical Pearls
- Myxedema coma is more common in elderly women, particularly during winter months 3
- The mortality rate remains high (30-60%) even with appropriate treatment
- The diagnosis is primarily clinical, and treatment should not be delayed while waiting for laboratory confirmation 4
- Presence of hypothermia in a patient with altered mental status should always raise suspicion for myxedema coma
- Patients may not have all classic signs of hypothyroidism, especially if the onset is acute
Treatment Considerations
Treatment must be initiated promptly in an intensive care unit setting with:
- Intravenous thyroid hormone replacement (levothyroxine and/or liothyronine)
- Glucocorticoid administration
- Supportive care including ventilation, warming, fluid management, and treatment of precipitating factors 5, 6
Early recognition of these signs is crucial as myxedema coma represents a true endocrine emergency with high mortality if treatment is delayed.