1. Clinical Assessment

Distinguishing the hypermetabolic state of thyroid storm from the hypometabolic state of myxedema coma requires a systematic evaluation of vital signs, mental status, and multi-organ findings. These two conditions represent opposite ends of the thyroid function spectrum, yet both are life-threatening emergencies.

A. Vital Signs

• Temperature: A hallmark differentiator. Thyroid storm typically presents with significant hyperthermia (>38.5°C), while myxedema coma is characterized by profound hypothermia (<35°C).
• Heart Rate: Tachycardia, often exceeding 140 bpm or presenting as atrial fibrillation, is classic for thyroid storm. In contrast, myxedema coma features marked bradycardia (<60 bpm).
• Blood Pressure: Hemodynamics are dynamic. Thyroid storm may begin with labile hypertension but can progress to refractory hypotension in decompensated states. Myxedema coma consistently presents with hypotension.

B. Neurologic Status

• Thyroid Storm: Patients often exhibit severe central nervous system (CNS) hyper-excitability, including agitation, delirium, psychosis, or seizures.
• Myxedema Coma: The neurologic exam reveals profound CNS depression, ranging from lethargy and stupor to frank coma. The Glasgow Coma Scale is a critical tool to assess the need for definitive airway management.

C. Organ System Findings

• Gastrointestinal (GI): Thyroid storm manifests with hypermotility (diarrhea, nausea, vomiting) and can lead to hepatic dysfunction. Myxedema coma causes hypomotility, leading to constipation or paralytic ileus, and is associated with marked elevation in creatine kinase (CK) from myopathy.
• Cardiopulmonary: High-output heart failure and pulmonary edema are common in thyroid storm. Myxedema coma can cause hypoventilation, pleural effusions, and pericardial effusions.

2. Laboratory Evaluation

Rapid laboratory analysis is crucial to confirm thyroid hormone derangements, identify potential precipitating factors, and detect critical metabolic complications, such as adrenal insufficiency.

A. Thyroid Function Tests (TFTs)

• Thyroid Storm: Characterized by a suppressed Thyroid-Stimulating Hormone (TSH) and elevated free thyroxine (T4) and free triiodothyronine (T3). The degree of free T3 elevation often correlates best with the clinical severity of the storm.
• Myxedema Coma: The classic pattern is a markedly elevated TSH with low free T4 and T3. However, TFTs must be interpreted cautiously in critically ill patients, as “euthyroid sick syndrome” can mimic these findings.

B. Adrenal Assessment

• A random cortisol level should be drawn immediately. A level <10 µg/dL is highly suggestive of relative adrenal insufficiency, a common concurrent finding.
• An ACTH level can be obtained for later diagnostic workup, but treatment with empiric hydrocortisone should never be delayed while awaiting results.

C. Metabolic Panels

• Electrolytes: Hyponatremia is a common and significant finding in myxedema coma due to impaired free water excretion.
• Glucose: Hypoglycemia can occur in myxedema coma due to impaired gluconeogenesis and is a marker of severe metabolic collapse. Glucose levels should be monitored closely.
• Liver Function Tests (LFTs) and Creatine Kinase (CK): Mild transaminitis can be seen in thyroid storm due to hepatic congestion and hypermetabolism. In contrast, a marked CK elevation is characteristic of the myopathy in myxedema coma.

3. Advanced Diagnostics

Electrocardiography (ECG) and imaging studies are essential to assess the end-organ impact of the thyroid emergency, identify complications, and guide the intensity of monitoring.

A. Electrocardiogram (ECG)

• Thyroid Storm: Common findings include sinus tachycardia, new-onset atrial fibrillation with a rapid ventricular response, and occasionally a shortened QTc interval.
• Myxedema Coma: The ECG typically shows sinus bradycardia, low voltage QRS complexes (due to myxedema and/or pericardial effusion), and a prolonged QTc interval, which creates a significant risk for torsades de pointes.

B. Imaging

• Chest X-Ray: Can reveal signs of heart failure such as pulmonary edema and cardiomegaly in both conditions. Pleural effusions are also common, particularly in myxedema coma.
• Echocardiography: This is a key diagnostic tool. In thyroid storm, it may show a hyperdynamic ventricle and signs of high-output heart failure. In myxedema coma, it can reveal global hypokinesis, diastolic dysfunction, and the presence of a pericardial effusion, which can progress to tamponade.

4. Severity Scoring Systems

Validated scoring systems are critical tools that translate a constellation of clinical and laboratory findings into objective, actionable categories that guide triage and define urgency.

A. Burch–Wartofsky Point Scale (BWPS) for Thyroid Storm

The BWPS is the most widely used tool for diagnosing and quantifying the severity of thyroid storm. Points are assigned across several domains, with a higher score indicating a greater likelihood and severity of storm.

• Total Score ≥45: Highly suggestive of thyroid storm.
• Total Score 25–44: Suggests impending storm; requires close monitoring and aggressive treatment.
• Total Score <25: Thyroid storm is unlikely.

B. Myxedema Coma Score (Popoveniuc et al.)

A similar scoring system exists for myxedema coma, incorporating key parameters of hypometabolism and organ dysfunction.

• Core Components: Temperature, CNS status, GI symptoms, cardiovascular hemodynamics, metabolic disturbances (hyponatremia, hypoglycemia), and the presence of precipitating factors.
• Interpretation:
  • Score ≥60: Diagnostic of myxedema coma.
  • Score 25–59: Indicates impending decompensation.
  • Score <25: Myxedema coma is unlikely.

5. Integration into a Clinical Pathway

Severity scores are the cornerstone of a modern clinical pathway for thyroid emergencies. They inform triage decisions, dictate monitoring intensity, and trigger time-sensitive interventions.

A. Triage and Monitoring

• ICU Admission: Patients with a BWPS ≥45 or a myxedema coma score ≥60 require immediate ICU admission for invasive hemodynamic monitoring (e.g., arterial line), continuous cardiac monitoring, and potential mechanical ventilation.
• High-Dependency/Step-Down Unit: Patients in the “impending” range (BWPS 25–44 or coma score 25–59) should be managed in a high-dependency setting with continuous telemetry and frequent reassessment.

B. Immediate Intervention Algorithm

Once a thyroid emergency is suspected, a standardized, parallel set of interventions should be initiated.