Primary Hypothyroidism Unleashing Severe Pericardial Effusion: Lessons Learnt From an Atypical Presentation of a Common Endocrine Condition

Primary hypothyroidism is a commonly encountered endocrine disorder and can be associated with pericardial effusion and cardiac tamponade in severe cases. Early detection of hypothyroidism is key since it is a potentially treatable and reversible cause of pericardial effusions. A 53-year-old female was admitted following a fall. The clinical history was remarkable, with symptoms of persistent tiredness and fatigue for six months. She had no known medical conditions and was not taking any regular medications. Vital signs were stable. Physical examination revealed bilateral pitting pedal oedema and a tense abdomen with shifting dullness. Cardiovascular and respiratory examinations were normal. Notably, the patient exhibited delayed relaxation of deep-tendon reflexes bilaterally at the patellar and ankle sites. Pertinent laboratory findings showed an elevated thyroid-stimulating hormone (TSH) level of 151.69 milliunits/L, a low free thyroxine (fT4) level of <5.4 pmol/L, a haemoglobin level of 85 g/L, and a markedly high anti-thyroid peroxidase antibody level of 957.35 IU/mL. An electrocardiogram revealed a normal sinus rhythm with a low-voltage QRS complex. Chest X-ray findings indicated cardiomegaly suggestive of left heart failure. An emergent transthoracic echocardiography (TTE) demonstrated a large pericardial effusion measuring 5.4 cm posterior to the left ventricle. The most likely aetiology in this case was severe primary hypothyroidism. She initially received intravenous liothyronine 10 micrograms every four hours, followed by oral liothyronine 5 micrograms twice a day in conjunction with levothyroxine 100 micrograms once a day. The adrenal reserve assessment was satisfactory. An urgent pericardiocentesis was performed, draining a total of 900 mL of serosanguinous fluid. Serial echocardiograms demonstrated the absence of residual effusion. Hypothyroidism is a relatively uncommon cause of pericardial effusion. By ensuring early detection and appropriate treatment, we can optimise patient outcomes and prevent potential complications associated with untreated hypothyroidism.