A 46 year-old Hispanic female with no past medical history, and no history of trauma presented to the hospital with complaints of shortness of breath worsening gradually over past two months. The patient’s physical examination was remarkable for diminished heart sounds at auscultation. A complete blood count chemistry was within normal limit. Collagen vascular profile was negative. A chest x-ray revealed enlarged cardiac shilloute suggestive of pericardial effusion. A computed tomography (CT) scan of chest showed massive pericardial effusion. A 2D-echocardiogram confirmed the massive pericardial effusion without any evidence of right ventricular collapse. Pericardiocentesis was performed draining 2800 ml of straw-colored fluid. Cultures and cytology of the pericardial fluid were negative. Additional blood workup revealed an elevated thyroid stimulating hormone level. The patient was started on thyroid replacement therapy and had an uneventful recovery.