OBJECTIVE: To investigate how North American thyroidologists assess and treat 
amiodarone-induced thyrotoxicosis (AIT) and to compare the results with those of 
the same questionnaire-based survey previously carried out among European 
thyroidologists.
DESIGN: Members of the American Thyroid Association (ATA) with clinical 
interests were sent by e-mail a questionnaire on the diagnosis and management of 
AIT, 115 responses were received from the United States and Canada, representing 
about one-third of ATA members with clinical interests.
RESULTS: The majority of respondents (91%vs. 68% in Europe, P < 0.05) see < 10 
new cases of AIT per year, and AIT seems less frequent than amiodarone-induced 
hypothyroidism (AIH) in North America (34% and 66% of amiodarone-induced thyroid 
dysfunction, respectively, vs. 75% and 25%, respectively, in Europe, P < 0.001). 
When AIT is suspected, in North America hormonal assessment is mostly based on 
serum free T4 (FT4) and TSH measurements, while serum free T3 (FT3) 
determination is requested less frequently than in Europe; thyroid autoimmunity 
is included in the initial assessment less than in Europe. Most commonly used 
additional diagnostic procedures include, as in Europe, thyroid colour-flow 
Doppler sonography, and to a lesser extent, thyroid radioactive iodine uptake 
and scan, but Europeans tend to request multiple tests more than North 
Americans. Withdrawal of amiodarone is more often considered unnecessary by 
North American thyroidologists (21%vs. 10% in Europe in type 1 AIT, P < 0.05, 
34%vs. 20% in type 2 AIT, P < 0.05). In type 1 AIT thionamides represent the 
treatment of choice for North Americans as well as for Europeans, but the former 
use them as monotherapy in 65%vs. 51% of Europeans (P < 0.05) who more often 
consider potassium perchlorate as an useful addition (31%vs. 15% of North 
Americans, P < 0.01). Glucocorticoids are the selected treatment for type 2 AIT, 
alone (62%vs. 46% in Europe, P < 0.05) or in association with thionamides 
(16%vs. 25% in Europe, P = NS). After restoration of euthyroidism, thyroid 
ablation in the absence of recurrent thyrotoxicosis is recommended in type 1 AIT 
less frequently by North Americans. If amiodarone therapy needs to be 
reinstituted, prophylactic thyroid ablation is advised by 76% in type 1 AIT, 
while a 'wait-and-see' strategy is adopted by 61% in type 2 AIT, similar to 
behaviour of European thyroidologists.
CONCLUSION: Similarities and differences exist between expert North American and 
European thyroidologists concerning the diagnosis and management of AIT. While 
differences reflect the frequent uncertainty of the underlying mechanism leading 
to AIT, similarities may represent the basis to refine the diagnostic criteria 
and to improve the therapeutic outcomes of this challenging clinical situation.