Endocrine Abstracts

Background: Amiodarone-Induced Thyrotoxicosis (AIT) is often difficult to treat despite several treatment modalities. We present a case of failure of medical treatment despite an initial improvement.

Case Presentation: A 24-year old man with a history of cyanotic heart disease (translocation of main arteries with failure of full correction of the defect) was admitted for cardiac assessment in view of qualification for possible heart transplant. History revealed about 13 kg weight loss over two months. He had been receiving amiodarone for at least a year. Investigations on admission revealed TSH<0.005µIU/ml (0.27-4.2), FT4>7.7ng/dl (0.93-1.7), FT3 31.66pg/ml (2-4.4), consistent with severe AIT. Titres of all thyroid antibodies were negative, with no focal lesions on thyroid ultrasound. Amiodarone was stopped while thiamazole 20 mg tds and prednisone 40 mg od were started. After 10 days there was a fall of FT3 to 21.66pg/ml, but FT4 remained>7.7ng/dl. Pulse methylprednisolone 500 mg iv twice a week was added. There was a fall in FT3 to 6.75pg/ml (FT4 7.58ng/ml), followed by a rebound increase in FT3 to 20.28 pg/ml (FT4>7.77 ng/ml). A decision was made to proceed to thyroidectomy, but in view of FT4 above upper assay limit, a course of plasmapheresis, combined with intravenous thiamazole (80 mg od) was instigated. Glucocorticoid treatment was continued. Following seven courses of plasmapheresis there was a fall of FT3 to 8.3 pg/ml, but FT4 remained>7.77 ng/ml. Furthermore, the patient developed high temperature and sepsis (Klebsiella oxytoca) one day before planned surgery. He responded to meropenemum and vamcomycin. Successful thyroidectomy was performed seven days later (FT3 18.2 pg/ml, FT4>7.77 ng/ml before thyroidectomy). He remains stable on thyroxine 100 ug od.

Conclusion: Thyroidectomy is often the only treatment option in severe AIT and appears reasonably safe even in cases of cyanotic congenital heart disease.