Myxedema coma

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  • Hypothyroidism + mental status changes/coma + hypothermia + precipitating stressor[1]
  • Majority of the patients will be > 60yo[2]
  • Occurs in 0.1% of patients with hypothyroidism
  • Mortality may be as high as 60%[3]
  • ~50% of cases become evident after admission
  • Severe hypothyroidism may be first time presentation of hypothyroid[4]


Clinical Features


  • Temperature <35.5°C (95.9°F).



  • Hypoventilation
    • Early respiratory support with intubation is necessary to prevent respiratory collapse
  • Hypercapnia
    • There is often diaphragmatic dysfunction that causes worsening hypoventilation. The dysfunction is reversed after thyroid hormone administration[6]
  • Hypoxia
  • Pleural Effusion
  • Upper airway obstruction from glottic edema, vocal cord edema, and macroglossia can complicate intubation.


  • Altered mental status/Coma due to CO2 narcosis
  • Coma is very rare
  • Pseudomyotonic "hung up" deep tendon reflexes
    • Particularly Achilles reflex
    • Relaxation phase of DTR twice as long as contraction phase

Differential Diagnosis



Lab Abnormalities


Respiratory Support

  • Early mechanical ventilation will prevent respiratory collapse and severe respiratory acidosis.

Fluid Resuscitation

  • Patients are often intravsascularly depleted and have an underlying infection mandating aggressive fluid resuscitation
  • In patients who are hyponatremia, be cautious with rapid correction of hyponatremia and choose an appropriate fluid
  • Hypoglycemic patients will require intravenous dextrose added into the fluids


  • Vasopressors will be ineffective without concomitant thyroid hormone replacement

Hormone Replacement

  • Hydrocortisone 100mg q8hr IV since there is also adrenal insufficiency present
    • Alternative: Dexamethasone 2-4mg q12hrs (will not affect cortisol level or ACTH stimulation test)
  • Levothyroxine (T4) (generally agreed upon first line therapy)
    • Dose: 100 to 500 mcg (4mcg/kg IV) followed by 75 to 100 mcg administered IV daily until the patient takes oral replacement.[7]
    • Does require extrathyroidal conversion which can be reduced in myxedema but will have a slow steady onset of action
    • Potentially safer in patients with CAD
    • American Thyroid Association recommends treatment with both T4 and T3[8]
  • T3 20mcg IV followed by 2.5-10mcg q8hr
    • Start with 10mcg if elderly or has CAD
    • Does not require extrathyroidal conversion
    • More rapid onset but may be harmful in patients with CAD


  • Treat with passive rewarming
  • Hypothermia will also reverse with thyroid hormone administration
  • Do not actively rewarm:
    • Usually are volume depleted
    • Rapid peripheral vasodilation may induce worsening hypotension


  • Admit to ICU

See Also


  1. Wall CR. Myxedema coma: diagnosis and treatment. Am Fam Physician. Dec 1 2000;62(11):2485-90.
  2. Davis PJ, Davis FB. Hypothyroidism in the elderly. Compr Ther. 1984;10:17–23.
  3. Arlot S et al. Myxoedema coma: response of thyroid hormones with oral and intravenous high-dose L-thyroxine treatment. Intensive Care Med. 1991;17:16–8.
  4. Nicoloff JT et al. A form of decompensated hypothyroidism. Endocrinol Metab Clin North Am. 1993;22:279–90.
  5. Mazonson PD et al. Myxedema coma during long-term amiodarone therapy. Am J Med. 1984;77:751–4.
  6. Martinez FJ et al. Hypothyroidism. A reversible cause of diaphragmatic dysfunction. Chest. 1989;96:1059–63.
  7. Smallridge RC. Metabolic and anatomic thyroid emergencies: a review. Crit Care Med. 1992;20:276–91
  8. Jonklaas J, Bianco AC, Bauer AJ, Burman KD, Cappola AR, Celi FS, et al. Guidelines for the treatment of hypothyroidism: prepared by the american thyroid association task force on thyroid hormone replacement. Thyroid. 2014 Dec. 24 (12):1670-751.