Myxedema Coma: Clinical Presentation and Symptoms
Myxedema coma is a life-threatening emergency characterized by altered mental status, hypothermia, bradycardia, hypoventilation, and cardiovascular instability in patients with severe, untreated hypothyroidism. 1, 2, 3, 4
Cardinal Clinical Features
Neurological Manifestations
- Altered mental status ranging from confusion to frank coma is the defining feature 1, 2, 3, 5, 4
- Mental status changes may progress from lethargy to stupor to complete unresponsiveness 3, 4
- Absence of brain stem reflexes can occur in severe cases, mimicking brain stem infarction 3
- Milestone regression may precede altered consciousness in pediatric cases 5
Cardiovascular Symptoms
- Profound bradycardia is characteristic and slow to respond to initial treatment measures 1, 2
- Hypotension requiring circulatory support 1, 3
- Heart block may develop 5
- Cardiovascular instability with potential for cardiac decompensation 5
Metabolic and Temperature Dysregulation
- Hypothermia is a hallmark feature, often severe and refractory to warming measures 1, 2, 3, 5
- Hypoglycemia frequently accompanies the presentation 1
- Hyponatremia is common 1
Respiratory Manifestations
- Hypoventilation leading to respiratory failure 1, 3
- Hypercarbia from inadequate ventilation 5
- Respiratory support is often required 3
Physical Examination Findings
- Generalized edema (myxedema) throughout the body 2, 3
- Nonpitting edema can occur in severe, long-standing cases 6
- Pericardial effusions may be present 6
Precipitating Factors
Myxedema coma typically occurs when severe, longstanding hypothyroidism is triggered by an acute physiologic stressor. 7, 2, 4
Common Triggers
- Sepsis and infection are major precipitants 1, 2
- Surgery represents a critical physiologic stressor 7, 4
- Trauma or injury can precipitate decompensation 7, 2
- Cold exposure 2, 4
- Myocardial infarction 4
- Cerebrovascular accidents 2
- Gastrointestinal bleeding 2
- Sedatives and anesthetics in poorly controlled hypothyroid patients 8, 4
- Radiation therapy to the neck region for any malignancy 7
Laboratory Abnormalities
- Severely elevated TSH (e.g., 144.46 mU/L in documented cases) 1
- Profoundly low free T4 (e.g., 3.4 pmol/L or <0.5 ng/dL) 1, 5
- Elevated infection markers when sepsis is the trigger 1
- Acute kidney injury 1
- Electrolyte derangements including hyponatremia 1
Critical Diagnostic Considerations
The diagnosis is often missed or delayed because patients may present without a known history of hypothyroidism. 2, 3 The condition can mimic other neurological emergencies such as brain stem infarction, making clinical suspicion essential 3.
A high index of clinical suspicion is required when encountering any patient with severe decompensated metabolic state including mental status changes, especially when accompanied by hypothermia. 3 The combination of altered mental status, hypothermia, bradycardia, and hypoventilation in the setting of severe hypothyroidism should immediately raise concern for myxedema coma 5.
Age and Population Considerations
- More common in older women with hypothyroidism, but can occur at any age 5
- Can occur in pediatric patients, particularly those with central hypothyroidism 5
- May present at the time of diagnosis of secondary hypothyroidism, not just with noncompliance in known primary hypothyroidism 5
Urgent Treatment Implications
Treatment must be initiated immediately upon clinical suspicion, even before laboratory confirmation, given the high mortality rate. 4 Intravenous liothyronine and oral levothyroxine should be started emergently 1, and stress doses of intravenous hydrocortisone must be administered simultaneously until adrenal insufficiency is excluded 8, 1, 5, 4.