Proportion of type 1 and type 2 amiodarone‐induced thyrotoxicosis has changed over a 27‐year period in Italy

Abstract

Over a 27-year period, the epidemiology of AIT changed, as the prevalence of type 2 AIT progressively increased and that of type 1 remained constant. Thus, under most circumstances, endocrinologists nowadays deal with type 2 AIT, which is a destructive thyroiditis, generally treated successfully with glucocorticoids. Although no additional treatment is usually required after the destructive process subsides, periodic assessment of thyroid function is warranted, because of the occurrence of hypothyroidism (up to 17%) during long-term follow-up of these patients.

Amiodaron i tarczyca

“…Histopathological examination of the thyroid gland confirms an inflammatory response as evidenced by infiltration by histiocytes follicular swelling and fibrosis [35]. It may be difficult to differentiate between these two types of AIT.…”

“…Typ 2 AIT pojawia się u pacjentów z prawidłową lub nieznacznie powiększoną tarczycą i wynika bezpośrednio z toksycznego działania AMIO (lub jodu), wywołując zapalenie tarczycy z rozpadem [24]. Badanie histopatologiczne tkanki tarczycowej może potwierdzić obecność procesu zapalnego, nacieki histiocytów oraz włóknienie [35]. Zdarza się, że różnicowanie obu typów AIT jest trudne.…”

“…Nie do końca znane są przyczyny tego stanu, należy wziąć pod uwagę fakt, że pacjenci kwalifikowani do leczenia AMIO są dokładnie badani w kierunku występowania chorób tarczycy w porównaniu z tym co było w przeszłości [35].…”

“…In a subset of patients with euthyroid chronic autoimmune thyroiditis, AMIO may trigger a destructive process leading to AIT type 2. Thus, positivity of thyroid autoantibody tests does not always support diagnosis of the type 1 AI [35,44]. Other parameters, such as interleukin-6, C-reactive protein, and thyroglobulin, are not useful in clinical practice [45].…”

“…Suppressed serum TSH and elevated serum fT4 and fT3 are seen in both main types of AIT and cannot differentiate these two forms. An increased (> 4) T4/T3 ratio is a common feature of destructive thyroiditis [43], but this is not useful in individual AIT patients because serum fT4 is relatively higher than fT3 in all of them, due to the inhibition of D1 [35]. The search for thyroid-directed autoantibodies (particularly TSH receptor autoantibody) is relevant mainly in AIT patients whose underlying and pre-existing thyroid disorder is Graves' disease [2].…”