What is the management of myxedema?

Diagnosis and Management of Myxedema

Myxedema coma is a life-threatening emergency requiring immediate hospitalization and aggressive treatment with intravenous thyroid hormone replacement, supportive care, and management of precipitating factors. 1

Clinical Presentation

Myxedema (Severe Hypothyroidism)

• Characteristic symptoms:
  • Weakness and fatigue
  • Cold intolerance
  • Mental and physical slowness
  • Dry skin with non-pitting edema
  • Typical facies (puffy face with periorbital edema)
  • Hoarse voice
  • Weight gain
  • Constipation
  • Hair loss 2, 3

Myxedema Coma (Decompensated Severe Hypothyroidism)

• Life-threatening manifestation with:
  • Altered mental status/coma
  • Hypothermia
  • Hypoventilation with hypoxemia and hypercarbia
  • Hypotension
  • Hyponatremia
  • Occurs most often in elderly women
  • Often precipitated by acute stressors (infection, MI, cold exposure, surgery) 4, 5

Diagnosis

1. Laboratory Testing:

   • TSH and Free T4 (primary diagnostic tests)
   • Elevated TSH with low Free T4 confirms primary hypothyroidism
   • Low/normal TSH with low Free T4 suggests central hypothyroidism 1

2. Additional Testing in Myxedema Coma:

   • Complete blood count
   • Comprehensive metabolic panel
   • Blood cultures if infection suspected
   • Cortisol level (to rule out adrenal insufficiency)
   • ABG (to assess respiratory status)
   • ECG (to evaluate for bradycardia, low voltage)

Management

Myxedema (Severe Hypothyroidism)

1. Levothyroxine (T4) Replacement:

   • Starting doses:
     • Adults <70 years without cardiac disease: 1.6 mcg/kg/day
     • Elderly patients or those with cardiac conditions: 25-50 mcg/day 1
   • Titrate dose based on TSH levels measured every 6-8 weeks
   • Target TSH: 0.5-2.0 mIU/L for most patients; 1.0-4.0 mIU/L for elderly 1

2. Monitoring:

   • Check TSH and Free T4 6-8 weeks after initiation or dose change
   • Once stable, monitor every 6-12 months
   • Watch for signs of overtreatment (tachycardia, tremor, insomnia, heat intolerance) 1

Myxedema Coma (Medical Emergency)

1. Immediate Management:

   • Admit to ICU
   • Secure airway, breathing, circulation
   • Warm patient gradually (avoid aggressive rewarming)
   • Correct electrolyte abnormalities, particularly hyponatremia
   • Identify and treat precipitating factors (infection, drugs, etc.) 1, 5

2. Thyroid Hormone Replacement:

   • First-line: Intravenous levothyroxine (T4)
     • Loading dose: 300-500 mcg IV
     • Maintenance: 50-100 mcg IV daily 1, 5
   • Alternative: If IV T4 unavailable, oral levothyroxine via nasogastric tube
     • Loading dose: 300-500 mcg
     • Followed by taper over 3-5 days 6
   • Some experts recommend adding T3 (liothyronine) due to impaired T4 to T3 conversion in severe illness
     • T3 dose: 5-20 mcg IV every 8 hours 5

3. Adjunctive Therapy:

   • Stress-dose glucocorticoids:
     • Hydrocortisone 100 mg IV every 8 hours until adrenal insufficiency excluded 1, 4
   • Supportive care:
     • Mechanical ventilation if needed
     • Vasopressors for hypotension
     • Empiric antibiotics if infection suspected
     • Careful fluid management (avoid volume overload) 5

Special Considerations

1. Cardiac Patients:

   • Start with lower doses of levothyroxine
   • Monitor for cardiac arrhythmias, angina, or heart failure
   • Consider cardiology consultation 7

2. Adrenal Insufficiency:

   • Always rule out or treat adrenal insufficiency before starting thyroid replacement
   • Thyroid hormone increases metabolic clearance of glucocorticoids and can precipitate adrenal crisis 7

3. Elderly Patients:

   • More susceptible to adverse effects of thyroid replacement
   • Start with lower doses (12.5-25 mcg/day)
   • Slower titration schedule
   • Target higher TSH (1.0-4.0 mIU/L) 1

Prognosis and Follow-up

• Myxedema coma carries a high mortality rate (30-60%) even with treatment
• Factors associated with poor prognosis include:
  • Advanced age
  • Delayed diagnosis and treatment
  • Severe hypothermia
  • Persistent hypotension
  • Multiple comorbidities 4, 5
• After recovery from myxedema coma, transition to oral levothyroxine maintenance therapy
• Regular monitoring of thyroid function is essential to prevent recurrence

Common Pitfalls to Avoid

1. Delaying treatment of suspected myxedema coma while awaiting laboratory confirmation
2. Starting thyroid replacement without ruling out adrenal insufficiency
3. Aggressive rewarming in hypothermic patients
4. Overhydration in patients with hyponatremia
5. Failure to identify and treat precipitating factors
6. Overly rapid correction of thyroid hormone levels in elderly or cardiac patients