# Out-of-Hospital Cardiac Arrest As the Initial Presentation of Myxedema Coma

## TL;DR

A rare case of myxedema coma presented as out-of-hospital cardiac arrest in a woman with undiagnosed hypothyroidism, highlighting the need for prompt endocrine evaluation in such cases.

## Contribution

This case report presents an exceptionally rare initial presentation of myxedema coma as out-of-hospital cardiac arrest.

## Key findings

- The patient exhibited profound hypothermia and bradycardia after cardiac arrest, with laboratory findings consistent with severe hypothyroidism.
- Despite treatment with high-dose thyroid hormone replacement, the patient's condition deteriorated due to complications like aspiration pneumonia and septic shock.
- The case underscores the importance of considering endocrine causes in cardiac arrest, particularly when TSH elevation is only modest.

## Abstract

Myxedema coma is a rare, life-threatening manifestation of severe hypothyroidism that typically presents in hospitalized patients with hypothermia, bradycardia, and altered mental status. In exceptionally rare instances, it may present with cardiac arrest as the initial manifestation.

We report a case involving a woman in her late 50s with obesity, obstructive sleep apnea, and previously undiagnosed hypothyroidism who experienced a witnessed out-of-hospital cardiac arrest. Following successful resuscitation, she was found to have profound hypothermia and bradycardia. Laboratory investigations revealed markedly decreased thyroid hormone levels with only modest elevation in thyroid-stimulating hormone. Her family reported a history of progressive lethargy, weight gain, cold intolerance, and confusion over several months. A prior elevated TSH had been documented one year earlier. Thyroid peroxidase antibodies were positive, while TSH receptor antibodies were negative.

She was treated with high-dose intravenous levothyroxine and liothyronine, in addition to intensive supportive care. Although her thyroid function improved biochemically and transient clinical improvement was noted, she developed aspiration pneumonia and progressed to septic shock, resulting in death on the fifth day of admission.

This case highlights the diagnostic challenge posed by myxedema coma, especially when TSH elevation is modest. Clinicians should maintain a high index of suspicion for endocrine causes of cardiac arrest and initiate prompt hormone replacement when indicated.