RESUMO
BACKGROUND: Thyrotoxicosis attributable exclusively to triiodothyronine (T3) is, by necessity, caused by accidental or intentional ingestion of pharmaceutical preparations. The clinical presentation of T3 overdose appears to differ from classic thyroid storm. CASE: A 30-year-old female patient presented serially to the emergency department with headache, nausea and vomiting. Neurological work-up was negative and she was treated for presumed viral gastroenteritis. Eventually she developed confusion and was admitted. Laboratory investigations showed a suppressed TSH and a free T3 above the linear range (>30â¯pmol/L), estimated by dilution in normal serum to be 330â¯pmol/L. She was diagnosed with thyrotoxicosis secondary to recently prescribed compounded liothyronine and was treated with seven rounds of plasmapheresis. Using a rapidly developed mass spectrometric method for T3, it was determined that compounding pharmacy had dispensed liothyronine at a concentration ≃ 1000 -times the prescribed dosage. CONCLUSION: The clinical and mass spectrometry laboratories played an essential role in the diagnosis of thyroid storm in this case of T3 overdose as the expected clinical features of hyperpyrexia, tachycardia and hypertension were initially absent.