Massive pericardial effusion without cardiac tamponade due to subclinical hypothyroidism (Hashimoto's disease)

Context Hypothyroidism is a significant cause of pericardial effusion. However, large pericardial effusions due to hypothyroidism are extremely rare. Hormone replacement therapy is the cornerstone of treatment for hypothyroidism and regular follow-up of patients after initiation of the therapy is indicated. Herein, the case of a 70-year-old woman with a massive pericardial effusion due to Hashimoto's disease is presented. Issues A 70-year-old female from a rural village on the island of Crete, Greece, was admitted to our hospital due to a urinary tract infection. She was under hormone replacement therapy with levothyroxine 100 mg once a day for Hashimoto's disease. Two years previously, the patient had had an episode of pericarditis due to hypothyroidism and had undergone a computed tomography-guided pericardiocentesis. The patient did not have regular follow-up and did not take the hormone replacement therapy properly. On admission, the patient's chest X-ray incidentally showed a possible pericardial effusion. The patient was referred for echocardiography, which revealed a massive pericardial effusion. Beck's triad was absent. Thyroid hormones were consistent with subclinical hypothyroidism: thyroid-stimulating hormone (TSH) 30.25 mIU/mL (normal limits: 0.25-3.43); free thyroxin 4 0.81 ng/dL (normal limits: 0.7-1.94). The patient had a score of 5 on the scale outlined by the European Society of Cardiology (ESC) position statement on triage strategy for cardiac tamponade and, despite the absence of cardiac tamponade, a pericardiocentesis was performed after 48 hours. The patient was treated with 125 mg levothyroxine orally once daily. Lessons learned This was a rare case of an elderly female patient from a rural village with chronic massive pericardial effusion due to subclinical hypothyroidism without cardiac tamponade. Hypothyroidism should be included in the differential diagnosis of pericardial effusion, especially in a case of unexplained pericardial fluid. Initiation of hormone replacement therapy should be personalised in elderly patients. TSH levels >10 mU/L usually require therapy with levothyroxine in order to prevent adverse events. Rural patients usually do not have regular follow-up after the initiation of hormone replacement therapy. Pericardial effusions due to hypothyroidism grow slowly and subclinical hypothyroidism rarely shows signs and symptoms and can be underdiagnosed. The ESC position statement on triage strategy for pericardial diseases is a valuable clinical tool to estimate the necessity for pericardial drainage in such cases.