What is the life-threatening hypothyroid condition in an older adult with a history of hypothyroidism, presenting with a stuporous state and elevated Thyroid-Stimulating Hormone (TSH) levels?

Myxedema Coma

The life-threatening hypothyroid condition you're describing is myxedema coma, characterized by stuporous or comatose mental status with severely elevated TSH levels, representing the most extreme manifestation of severe hypothyroidism with multiorgan system failure. 1, 2

Clinical Presentation

Myxedema coma presents with a constellation of severe findings that distinguish it from simple hypothyroidism:

• Altered mental status ranging from confusion to stupor to frank coma—note that the term "coma" is actually a misnomer, as patients can present with less severe mental status changes 1, 3
• Hypothermia is a cardinal feature, often profound and slow to respond to warming measures 1, 2, 4
• Bradycardia and hypotension, reflecting severe cardiovascular compromise 1, 2, 5
• Respiratory failure with carbon dioxide narcosis leading to coma—this is the common final pathway 1, 4
• Hyponatremia due to impaired free water clearance 1, 2

Laboratory Findings

• TSH levels are markedly elevated—the highest reported case showed TSH of 402.0 µU/L 3
• Free T4 is severely depressed, often unmeasurably low 2, 3
• The diagnosis cannot be established on laboratory tests alone—it is fundamentally a clinical diagnosis based on history and physical findings 1

Typical Patient Profile

• Elderly women are most commonly affected, as thyroid hypofunction is much more common in women 1
• May or may not have a history of previously diagnosed or treated thyroid dysfunction 1
• Often presents with a precipitating factor such as sepsis, infection, malnutrition, or medication non-compliance 2, 3

Critical Management Principles

Treatment must be initiated immediately in a critical care setting without waiting for confirmatory laboratory results, as mortality is high without aggressive early intervention. 1, 4

Immediate Treatment Protocol

• Intravenous levothyroxine should be started immediately—typical loading dose followed by daily maintenance 2, 5, 4
• Intravenous liothyronine (T3) should be added for rapid effect, as conversion of T4 to T3 is impaired in critically ill patients 2, 3
• Intravenous hydrocortisone must be given to prevent secondary adrenal insufficiency—this is critical and should be started before or concurrent with thyroid hormone 2, 5, 4
• Mechanical ventilation is often required for respiratory failure and CO2 narcosis 5, 4
• Vasopressor support may be necessary for cardiogenic shock and hypotension 5

Monitoring and Supportive Care

• Aggressive rewarming for hypothermia 2, 4
• Treatment of precipitating factors (infection, sepsis) with appropriate antibiotics 2
• Correction of electrolyte abnormalities, particularly hyponatremia 2
• Cardiac monitoring for bradycardia and potential cardiogenic shock 5

Common Pitfalls

• Delaying treatment while waiting for laboratory confirmation—treatment must begin as soon as myxedema coma is clinically suspected 1, 4
• Failing to administer corticosteroids before thyroid hormone—this can precipitate adrenal crisis 4
• Underestimating severity based on the term "coma"—patients with altered mental status short of frank coma still require aggressive treatment 3
• Missing the diagnosis in patients with atypical presentations, such as younger patients or those who are medication-compliant 5, 3

Prognosis

• Mortality remains high even with appropriate aggressive treatment 1, 5
• Outcome depends critically on time to treatment initiation—the faster treatment begins, the better the prognosis 4
• With prompt recognition and multipronged aggressive therapy, neurological status and thyroid function can return to normal over several days 5