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Hypothyroidism and Myxedema Coma Workup

  • Author: Erik D Schraga, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
Updated: Dec 11, 2015

Laboratory Studies

The following measurements and studies are indicated in hypothyroidism[6] :

  • Electrolytes
    • Hyponatremia is common secondary to extracellular volume expansion produced by elevated antidiuretic hormone.
    • Blood glucose level ranges from normal to low secondary to decreased gluconeogenesis and reduced insulin clearance.
    • Creatine phosphokinase (CPK), aspartate aminotransferase (AST) or serum glutamic oxaloacetic transaminase (SGOT), and lactate dehydrogenase (LDH) levels may be elevated in myxedema coma due to increased muscle membrane permeability. Creatine kinase (CK)-myocardial band (MB) levels are typically normal.
  • ABG: Hypoventilation commonly results in hypercapnia and hypoxia in patients with myxedema coma.
  • Urinalysis: Evaluate for source of infection.
  • Secondary studies
    • Thyroid function studies may not be immediately available to assist in clinical decision making in the ED.
    • Thyroid-stimulating hormone (TSH) is elevated in primary hypothyroidism, but it may be normal or low in secondary causes of hypothyroidism.
    • Free thyroxine (T4) levels are low.
    • Triiodothyronine (T3) resin uptake is decreased.
    • Free T4 index (T3 resin uptake x total serum T4) is low.
    • Critically ill patients may develop euthyroid sick syndrome, which must not be confused with a primary thyroid abnormality. These patients have low to normal TSH and T4 levels with low T3 levels.

Imaging Studies

See the list below:

  • Chest radiography
    • An enlarged cardiac silhouette in a chest radiograph may suggest pericardial effusion. A chest radiograph depicting a pericardial effusion is shown in the image below.
      Pericardial effusion. Note the "water-bottle" appePericardial effusion. Note the "water-bottle" appearance of the cardiac silhouette.
    • However, chest radiography is reported to have a 30% false-negative rate in detecting hypothyroid pericardial effusions.
    • Chest radiography can help detect pulmonary infections often associated with myxedema coma.
  • Acute abdominal series: An ileus may be associated with hypothyroidism, and it may be present in myxedema coma.
  • Head CT scan (noncontrast)
    • In patients with altered mental status, the scan may be helpful in ruling out other etiologies such as intracerebral hemorrhage.
    • The scan may be helpful in ruling out other etiologies of altered mental status, such as intracerebral hemorrhage.
  • Echocardiography: Perform this study if pericardial effusion is suspected.

Other Tests

See the list below:

  • Electrocardiogram
    • Bradycardia, low voltage, prolonged PR interval, T-wave abnormalities, and electrical alternans (suggestive of effusion) may be present.
  • Core temperature
    • Patients with myxedema coma have a temperature below 37°C (98.6°F) in 15% of cases.
    • Fifteen percent of those patients have a temperature below 29.5°C (85°F).
Contributor Information and Disclosures

Erik D Schraga, MD Staff Physician, Department of Emergency Medicine, Mills-Peninsula Emergency Medical Associates

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Howard A Bessen, MD Professor of Medicine, Department of Emergency Medicine, University of California, Los Angeles, David Geffen School of Medicine; Program Director, Harbor-UCLA Medical Center

Howard A Bessen, MD is a member of the following medical societies: American College of Emergency Physicians

Disclosure: Nothing to disclose.

Chief Editor

Romesh Khardori, MD, PhD, FACP Professor of Endocrinology, Director of Training Program, Division of Endocrinology, Diabetes and Metabolism, Strelitz Diabetes and Endocrine Disorders Institute, Department of Internal Medicine, Eastern Virginia Medical School

Romesh Khardori, MD, PhD, FACP is a member of the following medical societies: American Association of Clinical Endocrinologists, American College of Physicians, American Diabetes Association, Endocrine Society

Disclosure: Nothing to disclose.


Jerome FX Naradzay, MD, FACEP Medical Director, Consulting Staff, Department of Emergency Medicine, Maria Parham Hospital; Medical Examiner, Vance County, North Carolina

Jerome FX Naradzay, MD, FACEP is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

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Pericardial effusion. Note the "water-bottle" appearance of the cardiac silhouette.
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