What is the typical presentation of myxedema (severe hypothyroidism)?

Myxedema Presentation

Myxedema presents with a constellation of symptoms reflecting severe metabolic slowing, including weakness, cold intolerance, mental and physical slowness, dry skin, characteristic facial puffiness, and hoarse voice, with the most severe form—myxedema coma—manifesting as altered consciousness, hypothermia, bradycardia, and hypotension. 1

Clinical Features of Myxedema

Classic Symptoms

The typical patient with myxedema demonstrates:

• Weakness and fatigue (68-83% of cases)
• Cold intolerance
• Mental and physical slowness with cognitive impairment (45-48%), including memory loss and difficulty concentrating
• Weight gain (24-59% of cases)
• Dry skin and characteristic facial changes
• Hoarse voice
• Constipation 1, 2

Physical Examination Findings

The characteristic physical findings include:

• Typical myxedematous facies: facial puffiness and periorbital edema
• Non-pitting edema: generalized swelling due to interstitial deposition of hydrophilic mucopolysaccharides
• Bradycardia
• Hypothermia (in severe cases)
• Delayed deep tendon reflexes
• Thyroid gland enlargement (goiter) may be present depending on etiology 3, 1

Pathophysiology of Edema

The edema in myxedema is fundamentally different from typical fluid overload—it is largely a lymphatic edema caused by interstitial deposition of mucopolysaccharides, which leads to fluid and sodium retention plus impaired blood circulation and lymphatic drainage 3. This explains why the edema is typically non-pitting.

Myxedema Coma: The Life-Threatening Extreme

Myxedema coma represents the most severe, life-threatening manifestation of hypothyroidism with mortality rates up to 30%. 2 This is a true medical emergency requiring intensive care.

Presentation of Myxedema Coma

Patients typically present with:

• Altered mental status or coma (GCS often ≤8)
• Hypothermia (core temperature often <35°C)
• Hypotension and potential cardiogenic shock
• Bradycardia
• Hypoventilation with respiratory depression
• Hyponatremia (common finding)
• Extensive edema that may extend from lower limbs to abdomen 4, 5, 6

Precipitating Factors

Myxedema coma typically occurs when compensatory mechanisms are overwhelmed by:

• Infections (most common precipitant)
• Discontinuation of thyroid supplements (in known hypothyroid patients)
• Sedative drugs
• Cold exposure (though less important in tropical climates)
• Surgery or trauma 4, 5

High-Risk Populations

• Elderly women are most commonly affected
• Patients with multiple comorbidities (chronic kidney disease, heart disease)
• Those with undiagnosed hypothyroidism presenting for the first time 1, 6

Laboratory Findings

Thyroid Function Tests

• Markedly elevated TSH (often >99.9 mU/L in myxedema coma)
• Low free T4 (often <8 pmol/L in severe cases)
• Low free T3 6, 7

Associated Abnormalities

• Hyponatremia (impaired renal sodium reabsorption and reduced GFR)
• Elevated CK and myoglobin (secondary rhabdomyolysis in severe cases)
• Hyperlipidemia
• Anemia 3, 7, 2

Important Clinical Pitfalls

The diagnosis is often delayed because symptoms are nonspecific and overlap with chronic debilitating diseases common in elderly patients. 1 Maintain a high index of suspicion in:

• Any patient with unexplained hyponatremia—hypothyroidism should be in the differential diagnosis of every such case 4
• Elderly patients with progressive lethargy and confusion
• Patients with known hypothyroidism who present with altered mental status

Myxedema coma may be the first manifestation of previously undiagnosed hypothyroidism, particularly in elderly patients with multiple comorbidities where symptoms are attributed to other conditions 6.

Cardiovascular and Metabolic Complications

Untreated myxedema causes:

• Heart failure and increased cardiovascular event risk
• Insulin resistance and hyperglycemia in diabetic patients
• Menstrual irregularities (approximately 23%), including oligomenorrhea and menorrhagia
• Infertility and increased miscarriage risk 2

Predictors of Poor Outcome in Myxedema Coma

Significant mortality predictors include:

• Hypotension and bradycardia at presentation
• Need for mechanical ventilation
• Hypothermia unresponsive to treatment
• Sepsis
• Lower Glasgow Coma Scale scores
• High APACHE II and SOFA scores >6 5