Key Points
- Use the highest‑yield diagnostic test early; do not let testing delay time‑critical therapy.
- Set objective targets (hemodynamic, neurologic, respiratory) and reassess frequently.
- Plan definitive source control or disease‑specific therapy when indicated; document follow‑up and patient education.
Algorithm
- Suspect based on AMS, hypothermia, bradycardia, hyponatremia in known/suspected hypothyroidism.
- Draw TSH/free T4 and cortisol if feasible, but do not delay therapy.
- Give hydrocortisone 100 mg IV immediately; begin IV levothyroxine (± liothyronine in severe cases).
- Passive rewarming; careful ventilation to avoid rapid PaCO2 shifts; correct hyponatremia slowly.
- Search for and treat precipitants (infection, MI, sedatives); ICU monitoring with telemetry and electrolytes.
Clinical Synopsis & Reasoning
Severe decompensated hypothyroidism with hypothermia, bradycardia, hypotension, hyponatremia, and altered mental status. Treat empirically with stress‑dose glucocorticoids, IV levothyroxine loading (± liothyronine), passive rewarming, careful ventilation, and aggressive search for precipitants (infection, MI, sedatives).
Treatment Strategy & Disposition
Stabilize ABCs. Initiate guideline‑concordant first‑line therapy with precise dosing and continuous monitoring. Escalate to advanced/procedural interventions based on explicit failure criteria. Define ICU, step‑down, and ward disposition triggers; involve specialty teams early.
Epidemiology / Risk Factors
- Risk varies by comorbidity and precipitants; see citations for condition‑specific data.
Investigations
| Test | Role / Rationale | Typical Findings | Notes |
|---|---|---|---|
| TSH, free T4 (± T3) | Diagnosis | TSH high with low free T4 (primary) | Do not delay therapy |
| Cortisol (before steroids if feasible) | Rule out adrenal insufficiency | Low in concurrent AI | Give steroids regardless if high suspicion |
| BMP, ABG, CXR, ECG | Complications/precipitants | Hyponatremia, hypercapnia, effusions | Treat triggers |
Pharmacology
| Medication/Intervention | Mechanism | Onset | Role in Therapy | Limitations |
|---|---|---|---|---|
| Hydrocortisone 100 mg IV bolus → 50 mg q6h | Glucocorticoid | Minutes | Empiric coverage of possible AI | Taper once stable |
| Levothyroxine (T4) 200–400 µg IV load, then 50–100 µg IV daily | Thyroid hormone | Hours | Core thyroid replacement | Lower doses in elderly/CAD |
| Liothyronine (T3) 5–20 µg IV load then 2.5–10 µg q8h (selected) | Active T3 | Hours | Adjunct in severe cases | Arrhythmia risk |
| Passive rewarming, ventilatory support | Supportive | Immediate | Avoid active rewarming to prevent vasodilation | — |
Prognosis / Complications
- Outcome depends on timeliness of diagnosis and definitive therapy; monitor for complications.
Patient Education / Counseling
- Provide red‑flag education, adherence guidance, and explicit return precautions; arrange timely specialty follow‑up.
References
- Endotext: Myxedema Coma (updated) — Link