SHM Converge Scientific Abstract ePoster Gallery-Recurrent Syncope as an Isolated Presentation of Severe Primary Hypothyroidism

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This case report describes a 30-year-old man with two episodes of unexplained transient loss of consciousness, one with brief abnormal eye and arm movements and post-event confusion, raising concern for seizure. Initial evaluation for cardiac, neurologic, and metabolic causes was unrevealing: CBC, BMP, D-dimer, troponin, head CT, brain MRI, EEG, and echocardiogram were all normal. However, continuous telemetry showed intermittent sinus bradycardia, prompting further endocrine testing.<br /><br />Laboratory results revealed profound hypothyroidism, with a TSH of 326 mIU/L and a free T4 of 0.1 ng/dL, consistent with severe primary hypothyroidism. The patient was started on oral levothyroxine and had complete resolution of syncopal episodes, along with normalization of heart rate on follow-up.<br /><br />The report emphasizes that syncope occurs in about 1–2% of emergency department visits and is often evaluated for cardiac or neurologic causes, while endocrine causes may be missed. Severe hypothyroidism can lead to syncope through multiple mechanisms, including reduced adrenergic responsiveness, direct cardiac conduction effects such as sinus bradycardia or AV block, and cerebral hypoperfusion that may produce convulsive or “seizure-like” movements. This can result in misdiagnosis as epilepsy.<br /><br />The key takeaway is that severe hypothyroidism can present solely as recurrent syncope, even without classic symptoms. In patients with unexplained syncope after negative cardiac and neurologic workups, TSH is a low-cost, high-yield screening test. Early recognition and thyroid hormone replacement can prevent recurrence and reduce unnecessary testing.

Asset Subtitle

Nilesh Patel

Meta Tag

Author List Nilesh Patel

Category Clinical Vignettes

Concept Primary Hypothyroidism

Concept Syncope

Concept Seizure-like Activity

Concept Convulsive Syncope

Concept Thyroid-Stimulating Hormone

Distinguished Non-Finalist

Presenter Organization University of Tennessee Medical Center

Presenting Author Nilesh Patel

Track Adult

Keywords

severe hypothyroidism

syncope

sinus bradycardia

transient loss of consciousness

seizure-like movements

TSH

levothyroxine

cerebral hypoperfusion

primary hypothyroidism

endocrine cause

Primary Hypothyroidism

Syncope

Seizure-like Activity

Convulsive Syncope

Thyroid-Stimulating Hormone