Abstract Body (Do not enter title and authors here): Background:
Myocarditis is a cause of non-ischemic cardiomyopathy (NICM) and troponin elevation. There are many causes including uncontrolled thyroid disorder (TD). A thorough history, cardiac MRI (cMRI) followed by an endomyocardial biopsy (EMB) is necessary for diagnosis. This case illustrates a classic presentation of NSTEMI with a rare cause of myocarditis due to uncontrolled hypothyroidism.

Description of Case:
A 39-year-old female with history of congenital hypothyroidism and tobacco use disorder presented to the Emergency Department with sudden onset of unprovoked sub-sternal chest pain. She stated she had stopped taking her levothyroxine years ago due to side effects such as abdominal discomfort. On admission, work up included high sensitivity troponin (Hs-cTn), EKG, urine drug screen (UDS), and thyroid panel. There was no evidence of ischemic changes on EKG, Hs-cTn was 3600 (normal: 3-54) which up-trended to 43,742, and UDS was negative. She was placed on appropriate medical therapy for NSTEMI and taken for urgent coronary angiography wbich showed normal epicardial arteries. A transthoracic echocardiogram (TTE) was unremarkable with a normal ejection fraction (EF). However, she continued to complain of chest discomfort and palpitations. Her vital signs remained stable but her thyroid panel revealed a TSH of 127 (normal: 0.27-4.2), T4 of 0.18 (normal: 0.92 – 1.6) and T3 of 1.0 (normal: 2.3-4.2). Inflammatory markers were also elevated. A cMRI was obtained revealing gadolinium enhancement in the anterior septal wall with extension into the subepicardium of the inferior wall suggestive of possible myocarditis. An EMB was performed to elucidate etiology. Pathology results were only remarkable for edema but newly reduced EF of 30-35% was noted on TTE at time of biopsy. Endocrinology was consulted for untreated hypothyroidism and patient was initiated on levothyroxine leading to improvement of her symptoms.

Discussion:
Our patient's history and work up were consistent with myocarditis induced by severe hypothyroidism. TD is a rare cause of reversible NICM and symptoms improve once TD is controlled. While there are several cases reported on hyperthyroidism associated myocarditis, there are only a few cases of myocarditis associated with uncontrolled hypothyroidism. Clinicians should maintain a broad differential to ensure a thorough work up in a patient presenting with NSTEMI, and a thyroid panel should be included especially if myocarditis is suspected.