Hypothyroidism presenting as reversible multiple serous cavity effusions: a case report

Hypothyroidism is a known but frequently overlooked cause of reversible multiple serous cavity effusions, often leading to unnecessary invasive procedures and diagnostic delay. We report a 78-year-old man with a 5-month history of progressive abdominal distension, chest tightness, and dyspnea. Imaging revealed bilateral pleural effusion, moderate pericardial effusion, and massive ascites. Fluid analysis confirmed transudative effusions, while extensive workup for malignancy, infection, and heart failure was negative. Thyroid function tests subsequently revealed profound hypothyroidism (TSH 50 mIU/L). The patient was started on levothyroxine, and at one-month follow-up, the effusions markedly reduced with only small residual pleural and peritoneal fluid and significant symptomatic improvement. This case underscores the importance of thyroid function screening in patients with unexplained multiple serous effusions to avoid misdiagnosis and ensure timely effective therapy.