MON-426 New onset Graves disease leading to high output heart failure and pulmonary hypertension in a young individual

Abstract Disclosure: M. Herrera: None. J. Slusser: None. A. Ya: None. R. Nadeem: None. Introduction: Thyrotoxicosis results from excess production of thyroid hormones leading to a hypermetabolic state. High-Output Heart Failure is an uncommon type of Heart Failure (HF), characterized by elevated cardiac output (CO) greater than metabolic demand. Thyrotoxicosis-induced HF is a rare complication of thyrotoxicosis, generally seen in older patients with known cardiac abnormalities. We describe a case of a young female with decompensated HF and pulmonary hypertension secondary to new onset Grave’s disease. Case presentation: The patient was a 34-year-old female with past medical history of bipolar disorder who presented with two weeks of shortness of breath, orthopnea, and dyspnea on exertion. Vital signs were only remarkable for heart rate of 105 bpm. Initial lab work showed ALP 100 IU/L, AST 52 IU/L, ALT 36 IU/L, PROBNP 1,158 pg/mL, troponin 16 ng/L, and hgb 10.1 g/dL. Chest imaging revealed moderate cardiomegaly. ECG showed sinus tachycardia with possible atrial enlargement. She was diuresed and evaluated by cardiology. TTE showed eccentric left ventricular hypertrophy (EF 40 +/-5%), moderate tricuspid regurgitation, and moderate pulmonary hypertension (56mmHg). Sacubitril-valsartan and dapagliflozin were added to her regimen. Given unclear etiology for cardiomyopathy, patient underwent cardiac catheterization, which was negative for coronary artery disease, but demonstrated increased CO (Fick index 6.07 L/min/m2). At this point, thyroid function tests showed TSH <0.02 uIU/mL, Total T3 310 ng/dL, and Free T4 1.9 ng/dL. Upon further inquiry, patient referred two months of intermittent palpitations, 15 lb weight loss, progressive thyroid gland enlargement, and occasional swallowing discomfort. She denied prior personal or family history of thyroid disease. Physical exam revealed non-tender, diffusely enlarge thyroid (8 cm in height) with bilateral bruits and exophthalmos. Burch- Wartofsky scale resulted at 20 points, making thyroid storm an unlikely diagnosis. Further thyroid testing showed Anti-TpO Ab 600 IU/mL, TSH receptor Ab >40 IU/L, and TSI 288. Graves disease was diagnosed and decompensated HF was felt to be likely in the setting of high output secondary to hyperthyroid state. Patient was started on Methimazole 10mg twice a day and discharge with outpatient follow up with endocrinology and cardiology. Discussion/ conclusion: Thyrotoxicosis can lead to increased cardiovascular mortality in the setting of atrial fibrillation, heart failure, and tachycardia-induced cardiomyopathy. A high diagnostic suspicion for thyroid disorder is necessary in patients with new onset cardiovascular issues, especially in young and otherwise healthy individuals without signs and symptoms of overt thyroid storm. Presentation: Monday, July 14, 2025