What is the treatment for myxedema?

Treatment of Myxedema

Critical Distinction: Myxedema vs. Myxedema Coma

For severe myxedema coma (life-threatening emergency), intravenous thyroid hormone replacement is mandatory and oral levothyroxine is contraindicated due to unpredictable gastrointestinal absorption 1. However, for uncomplicated myxedema (severe hypothyroidism without coma), oral levothyroxine is the appropriate treatment 2.

Treatment Algorithm for Myxedema Coma

Immediate Stabilization (First Hour)

• Admit to intensive care unit immediately for aggressive supportive care 3
• Secure airway with intubation and mechanical ventilation if Glasgow Coma Score ≤8 3
• Correct hypoglycemia immediately if present 3
• Administer hydrocortisone 100 mg IV every 8 hours until adrenal insufficiency is ruled out - this must be done before or concurrent with thyroid hormone replacement to prevent acute adrenal crisis 3

Thyroid Hormone Replacement (Within First Few Hours)

• Intravenous levothyroxine is the standard of care for myxedema coma 3, 1
• The FDA explicitly warns that oral thyroid hormone products are not recommended for myxedema coma due to unpredictable absorption 1
• If IV levothyroxine is unavailable (common in resource-limited settings), oral levothyroxine can be effective: loading dose of 300-500 μg followed by taper over 3-5 days 4
• Combination therapy with levothyroxine 200 μg plus liothyronine 50 μg has shown efficacy in case reports 5

Supportive Care

• Passive rewarming for hypothermia (avoid active external warming which can cause vasodilation and cardiovascular collapse) 6
• Treat precipitating factors: antibiotics for sepsis/pneumonia, discontinue sedating medications 6
• Fluid resuscitation with caution (risk of hyponatremia worsening) 6
• Vasopressor support if hypotension persists 6
• Mechanical ventilation for hypercarbia and hypoxemia 6

Treatment Algorithm for Uncomplicated Myxedema (Without Coma)

Initial Dosing Strategy

• For elderly patients or those with cardiovascular disease: start with 25-50 μg levothyroxine daily 3
• For younger patients without cardiac disease: can start with higher doses 2
• The extreme caution in elderly patients is necessary because the transition from hypothyroid to euthyroid state increases cardiac workload 2

Monitoring and Titration

• Monitor TSH every 6-8 weeks while titrating to goal of TSH within reference range 3
• Typical maintenance dose is 1.6 μg/kg/day for patients without risk factors 3
• If cardiac symptoms develop or worsen, reduce the dose or withhold for one week and restart at lower dose 1

Critical Pitfalls and Caveats

Adrenal Crisis Risk

• Never initiate thyroid hormone replacement before ruling out or treating adrenal insufficiency - thyroid hormone increases metabolic clearance of glucocorticoids and can precipitate acute adrenal crisis 3, 1

Cardiovascular Complications

• Over-treatment may precipitate angina, arrhythmias, increased heart rate, and cardiac wall thickening, particularly in elderly patients and those with underlying cardiovascular disease 1
• Monitor for cardiac arrhythmias during surgical procedures in patients receiving suppressive therapy 1

Transition from IV to Oral Therapy

• Rare cases exist where patients remain refractory to oral therapy after initial IV treatment 7
• If decompensation occurs with transition to oral therapy, consider resuming IV therapy or investigating malabsorption 7

Drug and Food Interactions

• Levothyroxine has a narrow therapeutic index requiring careful dose titration 1
• Monitor for worsening glycemic control in diabetic patients - may require increased antidiabetic medications or insulin 1
• Certain medications and foods can affect levothyroxine absorption, requiring dose adjustments 1

Bone Health

• Over-replacement increases bone resorption and decreases bone mineral density, particularly in post-menopausal women 1
• Administer the minimum effective dose to achieve desired clinical and biochemical response 1