- 1 Background
- 2 Clinical Features
- 3 Differential Diagnosis
- 4 Evaluation
- 5 Management
- 6 Disposition
- 7 See Also
- 8 References
- Hypothyroidism + mental status changes/coma + hypothermia + precipitating stressor
- Majority of the patients will be > 60yo
- Occurs in 0.1% of patients with hypothyroidism
- Mortality may be as high as 60%
- ~50% of cases become evident after admission
- Severe hypothyroidism may be first time presentation of hypothyroid
- Bradycardia and hypothermia
- Cold exposure
- GI bleed
- Metabolic abnormalities (hypoxia, hypercapnia, hyponatremia, hypoglycemia)
- Medications: Beta blockers, sedatives, opioids, phenothiazine, amiodarone
- Medication non-adherence (thyroid meds)
- Temperature <35.5°C (95.9°F).
- Early respiratory support with intubation is necessary to prevent respiratory collapse
- There is often diaphragmatic dysfunction that causes worsening hypoventilation. The dysfunction is reversed after thyroid hormone administration
- 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
- TSH, FT4, FT3
- Blood cultures
- Cortisol level
- Bedside cardiac US for pericardial effusion
- Abnormal Thyroid Hormone Levels
- In primary hypothyroidism then TSH will be elevated and T4 and T3 will be low
- If the patient has secondary hypothyroidism (Pituitary dysfunction) the TSH can be low or normal and T4 and T3 will be low
- Elevated CPK
- Elevated creatinine
- Elevated transaminases
- Respiratory acidosis
- Early mechanical ventilation will prevent respiratory collapse and severe respiratory acidosis.
- 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
- 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.
- 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
- 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
- Wall CR. Myxedema coma: diagnosis and treatment. Am Fam Physician. Dec 1 2000;62(11):2485-90.
- Davis PJ, Davis FB. Hypothyroidism in the elderly. Compr Ther. 1984;10:17–23.
- 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.
- Nicoloff JT et al. A form of decompensated hypothyroidism. Endocrinol Metab Clin North Am. 1993;22:279–90.
- Mazonson PD et al. Myxedema coma during long-term amiodarone therapy. Am J Med. 1984;77:751–4.
- Martinez FJ et al. Hypothyroidism. A reversible cause of diaphragmatic dysfunction. Chest. 1989;96:1059–63.
- Smallridge RC. Metabolic and anatomic thyroid emergencies: a review. Crit Care Med. 1992;20:276–91
- 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.