(7.04) Myxedema Coma: The Forgotten Diagnosis

Severe hypothyroidism and myxedema coma can be evaluated with a single laboratory test, but these diagnoses are delayed when clinical suspicion is not high. With a reported mortality between 20% and 50% with treatment, these conditions are fatal if the diagnosis is missed. This case series presents two patients in which the timeline for checking serum thyroid stimulating hormone (TSH) impacted time to treatment and duration of severe life-threatening symptoms.

Case(s) Description :

Case 1: 69-year-old female with a history of hypothyroidism presented with one day of altered mental status. Evaluation showed hypoxemia to the 80s, heart rate of 49 beats/minute, and temperature under 35° C. Physical exam was significant for altered mental status and nonpitting edema. Labs were significant for TSH 285 mIU/L and free T4 0.14 μg/dL. Patient was started on IV levothyroxine and hydrocortisone in the intensive care unit (ICU). Mental status, bradycardia, and oxygenation improved within 24 hours of presenting to the hospital.

Case 2: 65-year-old male presented to the ED with 3 months of worsening fatigue, shortness of breath, intermittent slurred speech, and constipation. He was admitted for cardiac workup and discharged three days later after having a bowel movement and sodium rise from 123 mEq/L to 131 mEq/L. He presented 2 weeks later to a different hospital due to continued worsening symptoms. Evaluation showed normothermia, bradycardia to 58 beats/minute, and normotension (but with 20 mmHg systolic drop from baseline). Physical exam was significant for lower extremity nonpitting edema. Labs were significant for TSH 104 mIU/L and free T4 < 0.01 μg/dL. Patient was started on IV levothyroxine and hydrocortisone in the ICU. Bradycardia, shortness of breath, and slurred speech resolved within two days of treatment initiation, but treatment was started 17 days after his first presentation for medical care.

Discussion :

Thyroid disorders are missed when clinical suspicion is not high as the diagnosis requires specific lab tests. Myxedema coma presents with altered mental status, hypothermia, bradycardia, hypotension, hypoventilation, hyponatremia, and hypoglycemia that can lead to heart block, acute hypoxic respiratory failure, seizures, coma, and death. Higher degree of critical illness prior to treatment portends a higher mortality rate, and time to diagnosis after presentation directly impacts this.

We contrasted 2 cases of severe hypothyroidism in which a prompt vs. delayed diagnosis impacted the duration of severe symptoms and hospital course. Our cases highlighted the importance of prompt diagnosis and appropriate management of myxedema coma.