Diagnosis and management of amiodarone-induced thyrotoxicosis in Europe: results of an international survey among members of the European Thyroid Association.
OBJECTIVE
To determine how expert European thyroidologists assess and treat amiodarone-induced thyrotoxicosis (AIT).


METHODS
Members of the European Thyroid Association (ETA) with clinical interests were asked to answer a questionnaire on the diagnosis and management of AIT. A total of 124 responses were received: 116 from Europe, seven from USA and one from Brazil. After excluding responses coming from the same centre, 101 responses from 24 European countries were analysed, representing approximately 65% of clinically active European ETA members.


RESULTS
The majority of respondents (68%) see 1-10 new cases of AIT/year, and AIT seems to be more frequent than amiodarone-induced hypothyroidism in Europe, where in many instances iodine intake is borderline or moderately deficient. A good collaboration with cardiologists exists in most centres, and patients receiving chronic amiodarone treatment are checked for thyroid function most commonly every 4-6 months. When AIT is suspected, a diffuse or nodular goitre is present or in the absence of apparent abnormalities of the thyroid, free thyroxine (FT4), free triiodothyronine (FT3) and TSH are assayed by almost 90% of respondents. Thyroid autoimmunity is evaluated in the initial assessment by > 80%, while evaluation of urinary iodine excretion is unhelpful for > 60%. Most commonly used additional diagnostic procedures include thyroid ultrasonography, particularly colour flow Doppler sonography, and, to a lesser extent, a thyroid uptake scan. If the thyroid gland is apparently normal, measurement of thyroidal radioactive iodine uptake is considered useful by a large proportion of respondents to establish the destructive nature of the process. Differentiation of type I and type II AIT is difficult and, possibly, not correct for 27% of respondents, who believe that mixed (or indefinite) forms are probably more frequent than previously recognized. Approximately 10-20% do not consider amiodarone withdrawal necessary in the therapeutic strategy of AIT, especially if the thyroid gland is apparently normal. Most respondents (82%) treat type I AIT with thionamides, either alone (51%) or in combination with potassium perchlorate (31%), while the preferred treatment for type II AIT is represented by glucocorticoids (46%). Some respondents, in view of diagnostic difficulties, initially treat all cases of AIT with a combination of thionamides and glucocorticoids. After restoration of euthyroidism, ablative therapy is recommended by 34% in type I and only 8% in type II AIT. If amiodarone therapy needs to be reinstituted, prophylactic thyroid ablation is recommended by 65% in type I AIT, while a wait-and-see strategy is adopted by 70% in type II AIT.


CONCLUSIONS
Areas of certainty and uncertainty concerning AIT are present among expert European thyroidologists, both from a diagnostic and a therapeutic standpoint. Diagnostic criteria need to be refined in order to improve therapeutic outcome.
Bartalena
Luigi
L
Division of Endocrinology, University of Insubria, Varese, Italy. l.bartalena@libero.it
Wiersinga
Wilmar M
WM
Tanda
Maria Laura
ML
Bogazzi
Fausto
F
Piantanida
Eliana
E
Lai
Adriana
A
Martino
Enio
E
D000638:Amiodarone / Q000009:adverse effects*; D005060:Europe; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D011877:Radionuclide Imaging; D012680:Sensitivity and Specificity; D012955:Societies, Medical; D011795:Surveys and Questionnaires; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000000981:diagnostic imaging; D013963:Thyroid Hormones / Q000097:blood; D013965:Thyroidectomy; D013971:Thyrotoxicosis / Q000139:chemically induced* / Q000175:diagnosis* / Q000601:surgery; D018615:Ultrasonography, Doppler, Color; D014665:Vasodilator Agents / Q000009:adverse effects*
D007457:Iodine Radioisotopes; D013963:Thyroid Hormones; D014665:Vasodilator Agents; D000638:Amiodarone