SUN-367 Missed Opportunities in Myxedema Coma: The Critical Role of Early Thyroid Function Testing and IV Levothyroxine Administration

Abstract Disclosure: M. Shah: None. R. Devbhandari: None. O. Oluwatimilehin: None. R.M. Jhingan: None. Background: Myxedema coma is a life-threatening endocrine emergency caused by severe hypothyroidism, often exacerbated by infection, surgery, or malabsorption. Timely recognition and IV levothyroxine treatment are crucial to prevent multi-organ failure, particularly respiratory complications. This case underscores the importance of proactive thyroid function testing (TFT) in critically ill patients to prevent delays in ventilator weaning. Case Presentation A 72-year-old woman with chronic hypothyroidism, stable on levothyroxine 137 mcg daily, was hospitalized for acute respiratory failure. Differential diagnoses included pneumonia, CHF, and COPD exacerbation. The primary focus was on treating respiratory failure, and thyroid function was not initially considered. Despite elevated thyroid function tests (TSH 37 mIU/L - normal: 0.4-4.0 mIU/L, free T4 0.6 ng/dL - normal: 0.8-1.8 ng/dL, total T3 32 ng/dL - normal: 80-180 ng/dL, free T3 0.7 pg/mL - normal: 2.3-4.2 pg/mL), her levothyroxine dose was unchanged, and no repeat TFTs were performed. The patient required tracheostomy and PEG tube placement due to prolonged ventilator dependence. It remains unclear whether earlier TFTs could have facilitated earlier weaning from mechanical ventilation, potentially preventing the need for a tracheostomy.One month later, the patient was readmitted with profound bradycardia (HR 30s), hypotension (SBP 60-70 mmHg), hypothermia (32°C), and severe respiratory acidosis. TFTs confirmed severe hypothyroidism (TSH 108.3 mIU/L, free T4 < 3.0 ng/dL, total T3 20.1 ng/dL), confirming myxedema coma. The patient was treated with IV levothyroxine 200 mcg, hydrocortisone 100 mg, and epinephrine for circulatory support. Her condition improved, and antibiotics were discontinued the following day. Conclusion: This case highlights a gap in thyroid hormone management in a patient with chronic hypothyroidism and risk factors for decompensation, including severe illness and recent PEG tube placement. Failure to adjust levothyroxine dosing and repeat TFTs led to untreated hypothyroidism and prolonged ventilator dependence. Hypothyroidism impairs respiratory function, causing diaphragmatic weakness and reduced respiratory drive, complicating ventilator weaning. Earlier recognition and IV levothyroxine treatment could have facilitated earlier weaning, potentially preventing tracheostomy placement. Early thyroid hormone replacement reverses respiratory dysfunction, improving ventilator weaning and reducing the need for prolonged mechanical ventilation. This case underscores the importance of early TFTs and IV levothyroxine in critically ill patients to optimize recovery and avoid unnecessary interventions like tracheostomy. References: Gilani, A. A., et al. "Myxedema Coma - Diagnosis and Treatment." Chest, vol. 148, no. 6, 2015, pp. 1223-1232. Presentation: Sunday, July 13, 2025