Endocrine Abstracts

A 60-year-old engineer was reviewed in the Endocrinology clinic on 07/05/2021. He reported weight loss, palpitations, disturbed sleep, and fatigue over the previous four (4) months. He denied any neck pain or swelling. There were no symptoms consistent with thyroid eye disease. He had no pre-existing history of thyroid disease. TFT’s in March 2021 confirmed primary hyperthyroidism (TSH < 0.004 (0.35- 4.94 miu/l), FT4 19.8 (9-19 pmol/l), FT3 7.4 (2.9- 4.9 pmol/l). Anti-TSH receptor antibodies 0.43 (0-2 IU/l) and TPO antibodies were negative. His GP had started carbimazole 20 mg once daily at the end of March 2021 after discussion with the Endocrinology team. A thyroid uptake scan was requested to rule out toxic nodular disease. There was a long delay in obtaining the uptake scan but eventually he received an appointment from the nuclear medicine team approximately 5 months after the clinic appointment. In preparation for the scan his carbimazole was discontinued (September 2021) and serial repeat TFT’s revealed that his thyroid function had completely normalised despite remaining off carbimazole. Hence, he received a total of six (6) months of carbimazole treatment. The nuclear medicine team decided against proceeding with the scan as the diagnostic yield would be low. A thyroid ultrasound scan was normal, revealing no evidence of nodular thyroid disease. He had a history of atrial fibrillation and had been treated with amiodarone 200 mg once daily for approximately 15 months (13/03/2018 – 01/07/2019). He underwent successful DC cardioversion during this time, but there was recurrence of his atrial fibrillation when he developed thyrotoxicosis. He had normal TFT’s during treatment with amiodarone and one (1) year after stopping the drug. Amiodarone had been discontinued eighteen (18) months prior to presentation with thyrotoxicosis. At follow up he remained clinically and biochemically euthyroid, off antithyroid medication. A diagnosis of late onset Amiodarone Induced Thyrotoxicosis (AIT) was considered. He had not been treated with steroids.

Discussion: Amiodarone is an effective anti-arrhythmic drug with recognised toxic effects. There are case reports describing the onset of hyperthyroidism long after the discontinuation of amiodarone. This case highlights the need to consider the diagnosis of AIT in patients previously treated with this drug.