SUN-319 - “Suicidal Ideation as the Initial Presentation of Myxedema Coma: An Atypical Neuropsychiatric Manifestation of Severe Hypothyroidism”

Myxedema coma is a rare, life-threatening manifestation of severe hypothyroidism with high mortality if unrecognized. Although classically associated with decreased consciousness, atypical presentations may obscure diagnosis. Neuropsychiatric symptoms, including depression and suicidal ideation, can predominate and delay appropriate management.

We report a 66-year-old male with a history of head and neck cancer (in remission), hypertension, generalized anxiety disorder, and major depressive disorder (MDD) for two years, with acute worsening over two weeks prior to admission, culminating in suicidal ideation. He presented with progressive fatigue, apathy, weakness, and decreased oral intake. On examination, he was somnolent but arousable, with slowed mentation, flat affect, and psychomotor retardation. Vital signs revealed bradycardia (43 bpm) and hypothermia (36°C). Laboratory evaluation demonstrated hyponatremia, markedly elevated TSH (217 µIU/mL), and low free T4 (0.41 ng/dL), consistent with severe hypothyroidism. The myxedema coma diagnostic score was 60 points, confirming high diagnostic probability.

Treatment with intravenous levothyroxine, stress-dose hydrocortisone, and supportive care resulted in rapid clinical improvement, including resolution of neuropsychiatric symptoms.

This case underscores a critical diagnostic pitfall: severe hypothyroidism presenting primarily as acute psychiatric decompensation. Thyroid hormone deficiency alters central neurotransmission and cerebral metabolism, leading to mood disturbances that may rarely progress to suicidal ideation. Despite well-established systemic features, neuropsychiatric-dominant presentations remain underrecognized. Clinicians should maintain a high index of suspicion for thyroid dysfunction in patients with abrupt worsening of depression, particularly when accompanied by bradycardia, hypothermia, or hyponatremia. Early recognition is essential, as prompt thyroid hormone replacement is lifesaving and rapidly reversible.

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