Clinical experience of amiodarone‐induced thyrotoxicosis over a 3‐year period: role of colour‐flow Doppler sonography*

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Abstract
Summary: objective Current thinking is that amiodarone‐induced thyrotoxicosis (AIT) might be either iodine‐induced thyrotoxicosis in latent hyperthyroidism (Type 1) or destructive thyroiditis (Type 2), and also that colour‐flow Doppler sonography (CFDS) of the thyroid and serum interleukin 6 (IL‐6) are tools that can classify AIT and direct treatment. To assess the validity of this thinking, our objective was to determine whether CFDS and IL‐6 identified AIT subgroups with distinct features.design Retrospective case‐note audit of all patients presenting with AIT to the Endocrine Department of a UK teaching hospital over a 3‐year period. To assess proportions of Type 1 vs. Type 2 AIT and to compare and contrast their clinical features.patients 37 patients were identified with AIT (mean age 65, range 20–86 years). In 30 patients in whom AIT persisted, 25 underwent CFDS.results In 25 patients who underwent CFDS, 10 (40%) were classified as Type 1, 10 (40%) as Type 2 and 5 (20%) as indeterminate type. In the patients classified by CFDS in whom AIT persisted, 40% of Type 1 patients were male vs. 90% of Type 2 patients. Also, free T4 tended to be lower in patients presenting with Type 1 AIT (52·1 ± 7·5 pmol/l) compared to Type 2 (74·8 ± 8·1 pmol/l, P = 0·08), free T3 was lower (8·8 ± 0·9 vs. 15·6 ± 3·0 pmol/l, P = 0·03) and the cumulative amiodarone dose was lower (66 ± 20 vs. 186 ± 28 g, P = 0·002). We used less prednisolone to achieve euthyroidism in patients with Type 1 AIT whereas carbimazole doses were not different and the time to euthyroidism was the same in both groups (81 ± 21 vs. 88 ± 13 days). IL‐6 was raised in two patients with Type 1 and in one patient with Type 2 AIT.conclusions CFDS could characterize two distinct subtypes in patients with AIT. Conversely, IL‐6 seemed to be an unhelpful test in this context.