Symptoms of Myxoedema Coma
Myxoedema coma presents as a life-threatening emergency characterized by altered mental status, hypothermia, bradycardia, respiratory failure, and hyponatremia in patients with severe untreated hypothyroidism.
Cardinal Clinical Features
Neurological Manifestations
- Altered mental status ranging from confusion to profound coma is the defining feature, with progressive deterioration from mental slowness and drowsiness to complete unresponsiveness 1, 2, 3
- Decreased level of consciousness with physical and mental slowness preceding complete coma 2, 4
- Hyporeflexia and generalized weakness may be present 5
Cardiovascular Signs
- Bradycardia is a consistent finding, with heart rate often severely depressed 1, 4, 5
- Hypotension requiring vasopressor support 1, 2
- Heart failure with pericardial effusions 2, 5
- Heart block may occur in severe cases 3
Thermoregulatory Dysfunction
- Hypothermia is a hallmark feature, often severe and slow to respond to warming measures 1, 4, 5, 3
- Presentation typically occurs in winter months in older patients 4
Respiratory Compromise
- Respiratory failure with hypoventilation 4, 3
- Hypercarbia (elevated CO₂) due to decreased respiratory drive 4, 5, 3
- Hypoxemia requiring ventilatory support 4
- CO₂ narcosis may be the presenting feature 5
Metabolic and Electrolyte Abnormalities
- Hyponatremia is frequently present 1, 4
- Hypoglycemia may occur at presentation 1, 2
- Acute kidney injury with electrolyte derangement 1
Fluid Accumulation
- Pleural effusions (bilateral) 2, 5
- Pericardial effusions (often severe) 2, 5
- Ascites 5
- Anasarca (generalized edema) 2
Laboratory Findings
Primary Hypothyroidism Pattern
- Markedly elevated TSH (e.g., 144.46 mU/L) with severely depressed free T4 (e.g., 3.4 pmol/L) 1
- Elevated infection markers if precipitated by sepsis 1
Central Hypothyroidism Pattern (Critical Diagnostic Pitfall)
- Normal or low-normal TSH (e.g., 2.42 mU/L) despite severely low free T4 (e.g., 0.14 ng/dL) 2, 3
- This pattern occurs with panhypopituitarism and may delay diagnosis if only TSH is measured 2, 3
- Low ACTH levels may indicate concurrent adrenal insufficiency 2
Precipitating Factors
- Systemic infections, particularly pneumonia 4
- Sepsis 1
- Medication effects 4
- History of head trauma causing panhypopituitarism 2
- Noncompliance with thyroid hormone replacement 4
- Cold exposure (winter months) 4
Critical Diagnostic Considerations
In patients with suspected myxoedema coma and history of head trauma or pituitary disease, both TSH and free T4 must be measured, as normal TSH levels do not exclude central hypothyroidism and may result in missed diagnosis. 2, 3
The condition typically presents in older women but can occur at any age, including pediatric patients with central hypothyroidism 4, 3. The combination of altered mental status, hypothermia, bradycardia, and respiratory compromise in the setting of severe hypothyroidism (whether primary or central) constitutes a medical emergency requiring immediate intensive care unit admission and treatment 1, 4, 5, 3.