What is the clinical picture of myxedema coma?

Clinical Picture of Myxedema Coma

Myxedema coma presents as a life-threatening endocrine emergency characterized by the triad of altered mental status (ranging from confusion to coma), profound hypothermia, and cardiovascular collapse (bradycardia and hypotension), typically occurring in elderly women during winter months with precipitating factors such as infection, cold exposure, or medication use. 1, 2, 3

Cardinal Clinical Features

Mental Status Changes

• Altered consciousness progressing from lethargy and confusion to stupor and ultimately coma is the defining neurologic feature 1, 4, 2
• Mental status deterioration follows a common pathway of respiratory decompensation with carbon dioxide narcosis leading to coma 2
• True seizures are extremely rare in myxedema coma; when seizure-like activity occurs, strongly consider alternative diagnoses first (particularly hypoglycemia or myoclonus from metabolic encephalopathy) 1

Cardiovascular Manifestations

• Bradycardia is nearly universal 1, 5, 6
• Hypotension progressing to cardiogenic shock in severe cases 5, 6
• Severely reduced left ventricular ejection fraction from impaired myocardial contractility 5
• Pulseless electrical activity cardiac arrest can occur in the most severe presentations 5

Temperature Dysregulation

• Profound hypothermia (often the most striking physical finding) 1, 6, 2
• Hypothermia may be slow to respond initially to rewarming measures 6
• Winter months are the typical time of presentation 2, 3

Respiratory Compromise

• Respiratory failure requiring mechanical ventilation 1, 5, 3
• Hypercarbia and hypoxemia from hypoventilation 3
• Intubation indicated when Glasgow Coma Score ≤8 4

Laboratory and Metabolic Abnormalities

Thyroid Function

• Severely elevated TSH (often >100 mU/L) 6
• Markedly low Free T4 levels 6, 7
• The diagnosis cannot be established on laboratory tests alone and must be based on clinical presentation 2

Metabolic Derangements

• Hyponatremia (common and clinically significant) 1, 5, 3
• Hypoglycemia (must be corrected immediately as it can precipitate both coma and seizures) 1, 4
• Acute kidney injury 5, 6
• Electrolyte derangements 6

Patient Demographics and Precipitating Factors

Typical Patient Profile

• Elderly women are the most common demographic (thyroid dysfunction being much more common in women) 2, 3
• May or may not have a history of previously diagnosed hypothyroidism 2
• Can occur in younger patients with known hypothyroidism and precipitating factors 5

Common Precipitants

• Infection/sepsis (pneumonia and other systemic infections) 6, 3
• Cold exposure 7, 3
• Myocardial infarction 7
• Surgery 7
• Medications that suppress thyroid function or CNS 3
• History of collapse with prolonged immobility ("long lie") 6

Associated Conditions Requiring Evaluation

Concurrent Adrenal Insufficiency

• Must be ruled out before or during treatment, as thyroid hormone replacement can precipitate adrenal crisis 4
• Hydrocortisone 100 mg IV every 8 hours should be administered empirically until adrenal insufficiency is excluded 4

Pituitary Pathology

• Patients with history of pituitary tumor resection are at risk 5
• Central hypothyroidism may coexist 5

Critical Pitfalls to Avoid

• Do not wait for laboratory confirmation to initiate treatment—the diagnosis is clinical and therapy must begin immediately upon suspicion given the high mortality rate 2, 7
• Do not overlook hypoglycemia—check and correct glucose immediately as it can cause both coma and seizure-like activity in hypothyroid patients 1, 4
• Do not assume seizure-like movements are true seizures—assess for myoclonus from metabolic encephalopathy instead 1
• Do not start thyroid hormone replacement without concurrent glucocorticoid coverage—this can unmask or worsen adrenal insufficiency 4