Thyroid color flow doppler sonography and radioiodine uptake in 55 consecutive patients with amiodarone-induced thyrotoxicosis

Abstract

Amiodarone-induced thyrotoxicosis (AMT) is a life-threatening condition, the appropriate management of which is achieved by identifying its different subtypes. Type 1 AIT develops in patients with underlying thyroid abnormalities and is believed to be due to increased thyroid hormone synthesis and release; Type 2 AIT occurs in patients with a normal thyroid gland and is an amiodarone-induced destructive process of the thyroid. Management differs in the two forms of AIT, since Type 1 usually responds to combined thionamides and potassium perchlorate therapy, while Type 2 is generally responsive to glucocorticoids. Mixed forms, characterized by coexistence of excess thyroid hormone synthesis and destructive phenomena, may require a combination of the two therapeutic regimens. In this cross-sectional prospective study, 55 consecutive untreated patients, whose AIT was subtyped according to clinical and biochemical criteria, were evaluated to assess the specificity of color flow doppler sonography (CFDS) and thyroidal radioiodine uptake (RAIU) in the differential diagnosis of AIT. Sixteen patients (6 men, 10 women, age 66+/-13 yr), who had diffuse or nodular goiter with or without circulating thyroid autoantibodies, were classified as Type 1 AIT; 39 patients (27 men, 12 women, age 65+/-13 yr) with apparently normal thyroids were classified as Type 2 AIT. All Type 1 patients had normal or increased thyroidal vascularity on CFDS, while Type 2 AIT patients had absent vascularity (p<0.0001). Thirteen Type 1 AIT patients had inappropriately normal or elevated thyroidal 3-h and 24-h RAIU values (range 6-37% and 10-58%, respectively), in spite of elevated values of urinary iodine excretion; the remaining 3 patients (two with nodular goiter, one with a thyroid adenoma) had low 3-h and 24-h RAIU values (range 1.1-3.0% and 0.9-4.0%, respectively). The latter patients, who were unresponsive to the combination of methimazole and potassium perchlorate, became euthyroid after the addition of glucocorticoids. Thirty-eight Type 2 AIT patients had low 3-h and 24-h RAIU values (range 0.4-3.7% and 0.2-3.0%, respectively), but one had inappropriately normal 3-h and 24-h RAIU values (6% and 13%, respectively). In conclusion, CFDS can accurately distinguish between Type 1 and Type 2 AIT, and in general the CFDS pattern is concordant with the thyroid RAIU. However, in 4 out of 55 patients (7%) the thyroid RAIU was discrepant, probably reflecting the coexistence of Type 1 and Type 2 AIT. Thus, assessment of both CFDS and RAIU may provide a more accurate subtyping of AIT and help in selecting the appropriate therapy. Finally, in long standing iodine sufficient areas, such as the United States, where the thyroid RAIU is consistently low irrespective of the etiology of the AIT, CFDS offers a rapid and available method to differentiate between Type 1 and Type 2 AIT.

Amiodaron i tarczyca

“…However, conventional echography does not provide functional information, and the presence of goitre/nodules does not necessarily identify the mechanism responsible for AIT. Colour flow Doppler sonography may reveal normal/high vascularity (indicating hyperfunctioning gland) in most type 1 AIT or low/absent vascularity (damage to thyroid gland) in type 2 AIT [47,48]. Expertise in thyroid US is mandatory for proper evaluation.…”

“…Jednak tradycyjna sonografia nie daje informacji dotyczących czynności gruczołu, zaś obecność wola/guzków nie zawsze przesądza o mechanizmie AIT. Ultrasonografia z użyciem Dopplera może ujawnić prawidłowy/zwiększony przepływ (w gruczole nadczynnym) w większości przypadków AIT typu 1 lub zmniejszony/brak przepływu (rozpad gruczołu) w 2 typie AIT [47,48]. Ocena tarczycy w badaniu USG jest niezbędna dla prawidłowego rozpoznania.…”

Amiodarone-induced thyrotoxicosis: something new to refine the initial diagnosis?

“…The diagnostic uncertainty surrounding these forms of AIT is well reflected by recent questionnaire-based surveys carried out among expert thyroidologist members of the European Thyroid Association (9), Latin American Thyroid Society (10), and American Thyroid Association (11). In general, measurement of thyroidal radioactive iodine uptake (RAIU) and assessment by color flow Doppler sonography (CFDS) are considered the best tools to differentiate type 1 and type 2 AIT (12)(13)(14). In fact, RAIU usually is very lowto-suppressed in type 2 AIT and low-to-normal in type 1 AIT, while CFDS usually show a pattern 0 (absent vascularity) in type 2 AIT and a pattern I to III (normal-to-increased vascularity) in type 1 AIT.…”

Amiodarone-induced thyrotoxicosis: A review

“…A tool that is considered to be the best for rapid and early diagnosis of type 1 and 2 AIT is CFDS (19,20). This test determines the amount of blood flow within the thyroid and provides information about the morphology of the thyroid.…”

“…This test determines the amount of blood flow within the thyroid and provides information about the morphology of the thyroid. Eighty per cent of patients can be classified as having type 1 or 2 AIT by CFDS (19,20). The four major patterns are described in Table 2.…”