Decompensated Hypothyroidism: Why do we miss it, and how do we improve?
- Nov 30th, 2020
- Faiz Ahmed
Authors: Faiz Ahmed, MD (EM Resident Physician, Virginia Tech-Carilion Clinic) and Brian Meier, MD, MSc-GH (EM Attending, Carilion Clinic) // Reviewed by: Andrew Grock, MD; Alex Koyfman, MD (@EMHighAK); Brit Long, MD (@long_brit)
A 75-year-old female is brought to the Emergency Department (ED) by emergency medical services (EMS) for altered mental status. Vital signs include BP 87/64, HR 55, T 92.6 rectal, RR 12, SpO2 95% on room air. She is oriented to person only with a GCS of 12. She is found to be bradycardic and her extremities are cool with bilateral non-pitting edema on both legs. Her husband is en route but currently unreachable for further history.
Decompensated hypothyroidism AKA Myxedema Coma is a diagnosis we must recognize early in the ED as delayed or missed diagnosis carries significant mortality and morbidity.[1,2,3] Unfortunately, it is incredibly easy to miss as it commonly presents with a constellation of nonspecific symptoms similar to many common ED chief complaints. Due to the thyroid’s varied affects, hypothyroidism can affect a vast array of organ systems.
Typically, a patient maintains homeostasis until a precipitating event induces decompensated hypothyroidism (Table 1). It is most often seen in female elderly patients and tends to occur during the winter months.
There are a wide variety of precipitating causes, listed in Table 1. Infection is one of the most common causes.
While decompensated hypothyroidism presenting symptoms vary significantly, some main features typically remain consistent.
1. Altered Mental Status: Though often called ‘Myxedema Coma’, decompensated hypothyroid patients rarely present in a true coma. Instead they typically present altered, lethargic, or delirious.[5,7]
2. Low and Slow: Patients are typically hypothermic, bradycardic, hypotensive, hypoxemic, hypercapnic, and hypoglycemic. Hypothermia is extremely common in decompensated hypothyroidism. Be aware that a normal temperature in a decompensated hypothyroid patient is actually concerning for an underlying infection. The loss of thyroid hormone typically results in decreased HR and loss of motor tone. Hypotension is often refractory to both volume resuscitation and vasopressors. The hypotension does not resolve until thyroid hormone administration. Respirations are slow with low tidal volumes, which may lead to both hypoxia and hypercapnia and pending respiratory failure. Hypoglycemia can also occur.
3. Precipitating event: Precipitating events often require treatment. Focusing solely on the decompensated hypothyroidism may miss a treatable and reversable underlying pathology.
4. History of hypothyroidism: While some decompensated hypothyroidism patients may have no previous history of hypothyroidism others may already have been diagnosed previously. [8,9] An anterior midline neck scar, history of radioactive iodine ablation, or levothyroxine on the medication list all indicate of a history of hypothyroidism. 
The initial work-up consists of TSH and free T4 to evaluate thyroid function. Hypothyroidism typically presents with an elevated TSH and a decreased T4. More rarely, the hypothyroidism is due to a central etiology, which would result in a low TSH and a low T4. Concurrently the physician should evaluate the patient for both a precipitating factor and derangements resulting from the hypothyroidism (see list below). Additional tests may also be warranted based upon the clinical picture.[1,4,13]
- Metabolic panel
- Blood and urine cultures
- Cortisol level
- Head CT
Although the TSH and T4 may aid in the diagnosis of hypothyroidism the levels of these tests do not determine whether the patient is in compensated vs. decompensated hypothyroidism.[4,14] Decompensated hypothyroidism is a clinical diagnosis, and once suspected the provider should immediately begin treatment.
The initial treatment consists of the typical ED evaluation of large bore IVs, supplemental oxygen as needed, and cardiac monitoring as well as evaluation and stabilization of the airway, breathing, and circulation. These patients can be a difficult airway due to lingual edema and the physiologic derangements. After a primary and secondary survey reveals a clinical suspicion for decompensated hypothyroidism, the next step is to identify and treat the precipitating factors as listed above. One should strongly consider empiric antibiotics administration, as infection is often the common underlying precipitant. Vasopressors may also be used if indicated, however it is important to note that they may be ineffective without thyroid hormone replacement. Begin resuscitation with IV fluids and glucose.
Though thyroid hormone replacement should be administered immediately once the diagnosis is suspected, with 100 mg of stress dose IV hydrocortisone recommended as well. Since the hypothyroidism may be associated with adrenal insufficiency, thyroid replacement without steroids could lead to an adrenal crisis. [4,15] Laboratory results are not needed prior to treatment.
IV thyroxine (T4) with the dose of 4mcg/kg, typically between 100-500 mcg is the first line treatment. The levothyroxine IV doses are then tapered over the following days until patient can tolerate oral medications. Elderly patients or those at risk for cardiac side effects should be given doses on the lower end, while otherwise healthy patients can receive doses on the higher end of the dose range.[4,15]
IV triiodothyronine (T3) with the loading dose of 20 micrograms followed by 10 micrograms every 8 hours until patient is conscious is another regiment used. It is used as a second line agent or as an adjunct to T4 administration. This is typically reserved for patients who are critically ill or do not respond to initial T4 administration. [4,15]
T4 is the preferred first line agent as T3 may precipitate cardiac arrythmias in patients with underlying cardiac disease. [1,4,15]
So how often do we really miss this diagnosis and why?
Limited studies have evaluated the prevalence of missed decompensated hypothyroidism diagnosis in the ED. However, one study demonstrated only 21% of primary overt hypothyroidism was diagnosed in the ED with median time to diagnosis being 3 days. Of patients found to be in decompensated hypothyroidism only 50% were initially diagnosed in the ED.
The ambiguity and non-specific symptoms seen in both compensated and decompensated hypothyroidism likely contribute to the difficulty in obtaining the diagnosis. Another complicating factor is that the precipitating cause may reasonably explain the patient’s presentation. By recognizing and treating the precipitating cause, the physician may miss the additional overt and decompensating hypothyroidism. Although it is imperative to treat the precipitating event, the mortality of missing decompensated hypothyroidism can reach 100% if left untreated. These mistakes may be amplified in the ED due to increased anchoring bias due to its fast-pace.
How do we improve?
As this rare disease can mimic many others, the diagnosis is extremely difficult. Remember that hypothyroidism is a laboratory diagnosis, but decompensated hypothyroidism is a clinical diagnosis. It must be considered even in patients with multiple non-specific complaints if they fit the disease profile. One should also consider the demographics and time of year, as the classic decompensated hypothyroidism case is that of a confused, hypothermic, and hypotensive elderly woman presenting during the winter months. Lastly, a history of hypothyroidism or midline anterior neck scar should also raise clinical suspicion for this disease. Once suspected, immediately treat with stress dose steroids and IV T4. Provide IV antibiotics, as patients typically have an underlying infection. Be careful rushing to intubate these patients, as they have physiologically and anatomically difficult airways.
Our patient described above is an elderly female, presenting in winter, found to be altered, bradycardic, hypotensive, hypothermic, and with myxedema. Her symptoms are highly concerning for decompensated hypothyroidism. After a primary and secondary survey, she requires evaluation and treatment for both a precipitating event and her decompensated hypothyroidism. She requires treatment with stress dose steroids and 200 micrograms of IV T4 and admission to the ICU.
- Consider decompensated hypothyroidism in anyone with altered mental status associated with hypothermia, bradycardia, and hypotension, especially for an elderly female in the winter months.
- Work up and treat both the precipitating event and the hypothyroidism simultaneously.
- The diagnosis of decompensated hypothyroidism is DO NOT wait for laboratory confirmation to initiate treatment.
- First line treatment is with IV Hydrocortisone (100mg) and IV thyroxine (T4) 100-400 mcg.
From Dr. Katy Hanson at Hanson’s Anatomy:
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- Ono Y, Ono S, Yasunaga H, Matsui H, Fushimi K, Tanaka Y. Clinical characteristics and outcomes of myxedema coma: Analysis of a national inpatient database in Japan. J Epidemiol. 2017;27(3):117-122. doi:10.1016/j.je.2016.04.002
- Tintinalli JE, Ma OJ. Endocrine Disorders. In: Tintinalli’s Emergency Medicine: a Comprehensive Study Guide. New York, NY: McGraw-Hill; 2020.
- Wiersinga WM. Myxedema and Coma (Severe Hypothyroidism) [Updated 2018 Apr 25]. In: Feingold KR, Anawalt B, Boyce A, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279007/
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