12598 Tides of the Thyroid: Myxedema Ascites Unveiled

Abstract Disclosure: E. O'Neal: None. D. Duong: None. M. Caplan: None. K. Bird: None. Background: Primary hypothyroidism is a common clinical condition, complicated by ascites in less than 4% of cases. Myxedema ascites, caused by hypothyroidism, is also a rare cause of ascites in less than 1% of new onsets. Clinical Case: We present a 78-year-old female who initially presented to the hospital for abdominal swelling. CT of the abdomen/pelvis revealed a large amount of ascites in the abdomen and pelvis, along with bilateral pleural effusions. Labs were remarkable for a TSH level of 149 uIU/mL and a free T4 level of 0.41 ng/dL. A review of the patient’s chart showed a period of hyperthyroidism in 2022, and the patient had been placed on methimazole 10 mg by mouth daily. After several months, the patient transitioned to hypothyroidism. Methimazole was discontinued and levothyroxine was initiated. Improper medication reconciliation later occurred when she was admitted into a nursing home, causing the patient to be on methimazole and levothyroxine concomitantly in the outpatient setting. During the patient’s hospitalization, three liters of ascitic fluid were removed via ultrasound-guided paracentesis. The etiology of hypothyroidism-induced ascites includes multiple theories. This unique phenomenon can be explained by the following: increasing capillary permeability due to low levels of circulating thyroid hormone, formation of hyaluronic acid-albumin complexes, low nitric oxide, increased Vascular Endothelial Growth Factor, and diminished free water clearance due to excess Antidiuretic Hormone. When capillary permeability is elevated, this allows for protein extravasation. Lymphatic homeostasis becomes compromised, and this leads to the development of ascites. Investigations for this condition include an abdominal paracentesis and ascitic fluid analysis, which demonstrates an elevated protein count and lymphocyte count, with variability in leukocyte count and serum-ascites albumin gradient. Treatment for this reversible condition requires adequate thyroid replacement therapy. Our patient’s levothyroxine was increased to 100 mcg by mouth daily, and the patient demonstrated an appropriate response with monitoring of TSH. Discussion: Although ascites is typically thought to be of hepatic or cardiac origin, it is important to remember to rule out other potential causes such as thyroid disease. Reference: [1] Khalid, S., Asad-Ur-Rahman F., Abbass, A., Gordon, D., Abusaada, K. Myxedema Ascites: A Rare Presentation of Uncontrolled Hypothyroidism. Cureus 2016 Dec;8(12); e912. Presentation: 6/2/2024