FRI502 Myxedema Coma With An Unusual Pattern Of Thyroid Function Tests Due To Amiodarone-induced Hypothyroidism
Authors: Nguyen Son , Force Bahar , Schneider Aguirre Rebecca 
Published: October 2023

Disclosure: S. Nguyen: None. B. Force: None. R. Schneider Aguirre: None.

Introduction: Myxedema coma is an endocrine emergency characterized by severe hypothyroidism resulting in altered mental status or coma, hypothermia, cardiovascular compromise, pulmonary edema or pleural effusions, and/or gastrointestinal hypomotility, classically in the context of an elevated TSH and low thyroxine levels. Amiodarone use is associated with alteration of thyroid function tests and could cloud the laboratory presentation of myxedema coma. Here we present a case of myxedema coma in a patient with amiodarone-induced hypothyroidism with an elevated free T4 (FT4) and low total T3 (TT3). Clinical Case: A 64-year-old female with a history of chronic systolic heart failure, persistent atrial flutter treated with amiodarone, cerebrovascular accident, hypertension, chronic kidney disease stage 4, but not hypothyroidism, presented with constipation, confusion and lethargy worsening over 3 days. On initial evaluation, she was minimally responsive, hypothermic to 95.6 °F and bradycardic to low 50s. She was intubated for airway protection and vasopressors were started due to concern for cardiogenic shock. Exam was notable for coarse facial features, edema and cold extremities. A bedside echocardiogram showed reduced cardiac function from baseline. Her TSH was 40.65 uIU/mL (RR, 0.45-5.33 uIU/mL), FT4 1.79 ng/dL (RR 0.64-1.42 ng/dL), total T4 14.30 mcg/dL (RR 6.09-12.23 mcg/dL), TT3 70 ng/dL (RR 87-178 70 ng/dL). Sodium was 135 mmol/L (RR 136-145 mmol/L), serum glucose was 42 mg/dL, (RR 70-110 mg/dL), and eGFR was 18 mL/min/1.73 m2 (baseline eGFR 28 mL/min/1.73 m2). Evaluations for myocardial infarction and infectious etiology were initiated and ultimately negative. While elevated FT4 is not characteristic of myxedema coma, the overall constellation of stupor, constipation, bradycardia, hyponatremia, hypoglycemia, decreased eGFR and decreased cardiac function, in the setting of an elevated TSH and low TT3, made the diagnosis of myxedema coma extremely likely. The patient was started on levothyroxine 200 mcg IV daily and hydrocortisone 100 mg IV every 8 hours. After 16-20 hours on this regimen, the patient was weaned off sedation and vasopressors, extubated, and recovered baseline mental status. Hydrocortisone was stopped and on day 3 of hospitalization, she was transitioned to oral levothyroxine 88 mcg daily. Due to premature ventricular contractions her dose was decreased to 50 mcg orally daily five days after her initial presentation to the hospital. During this time, the TSH decreased to 3.59 uIU/mL and the FT4 rose to 2.83 ng/dL. Conclusion: We conclude that in patients treated with amiodarone, myxedema coma can still occur even if T4 levels are normal or elevated, likely due to decreased T4 to T3 conversion. In these cases, elevated TSH and a clinical picture consistent with severe hypothyroidism are more reliable indicators if the (free) T4 levels are unexpectedly elevated.

Presentation: Friday, June 16, 2023