Amiodarone Iodine‐induced Hypothyroidism: Risk Factors and Follow‐up in 28 Cases

Abstract

Amiodarone, an iodine-rich drug widely used for the treatment of cardiac tachyarrhythmias, may induce either hyperthyroidism or hypothyroidism. Of 467 patients chronically treated with this drug referred to our institution, amiodarone iodine-induced hypothyroidism (AIIH) developed in 28 patients (6%). AIIH patients were subdivided into two groups according to the presence (group A) or absence (group B) of underlying thyroid abnormalities. Thyroid autoantibodies were present in 10 of 19 patients from group A and 0 of 9 patients from group B. The thyroid 24-h radioiodine uptake (RAIU) was evaluated in 15 patients: low values (less than 4%) were found in three patients and detectable values (7-50%) were observed in 12. Perchlorate discharge tests were positive in all four patients tested. Follow-up data were available in 20 patients (16 in group A and four in group B). Hypothyroidism was transient in 12 (60%) and persistent for several months after amiodarone withdrawal in eight (40%). While all patients in group B had transient hypothyroidism, 50% of patients with underlying thyroid abnormalities (group A) had persistent hypothyroidism. Thyroid autoantibodies were found in seven of eight patients with persistent hypothyroidism and in only three of 12 patients with transient hypothyroidism. Conversely, seven of 10 patients with positive thyroid autoantibodies had persistent hypothyroidism and 9 of 10 patients with undetectable thyroid autoantibodies had transient hypothyroidism. These data indicate that: (i) AIIH may develop in patients with or without underlying thyroid abnormalities; (ii) RAIU is inappropriately elevated in many patients with AIIH; (iii) intrathyroidal iodine is not organified; (iv) serum thyroid autoantibodies represent a risk factor for the development of AIIH; (v) AIIH spontaneously remits after amiodarone withdrawal in patients without thyroid abnormalities, but may persist in patients with concomitant thyroid disorders, especially those with circulating thyroid autoantibodies.

Amiodaron i tarczyca

“…Niedoczynność tarczycy indukowana Amiodaronem może spontanicznie ustępować, zwłaszcza w przypadku braku autoimmunizacyjnej choroby tarczycy [94]. Według badań klinicznych, wskaźnikami ryzyka rozwoju niedoczynności tarczycy indukowanej AMIO są: wyjściowe stężenie TSH w surowicy > 1,4 mU/l, funkcja lewej komory EF < 45% oraz cukrzyca [95,96]. Należy również pamiętać, że leczenie AMIO per se, nawet w przypadkach bez niedoczynności tarczycy, wiąże się ze wzrostem stężenia TSH i niższym stężeniem fT3, bradykardią, a także zwiększonym stężeniem cholesterolu całkowitego i frakcji LDL.…”

“…AIH may, however, spontaneously remit, especially in the absence of underlying thyroid autoimmune disease [94]. According to clinical investigations, the predictors for AMIO-associated hypothyroidism were: baseline serum TSH levels > 1.4 mU/L, left ventricular function < 45%, and diabetes mellitus [95,96]. It should be kept in mind that AMIO treatment per se, in the absence of hypothyroidism, is associated with increased TSH levels and lower fT3 levels, bradycardia, and also increased total and LDL cholesterol levels.…”

Amiodarone compared with iodine exhibits a potent and persistent inhibitory effect on TSH-stimulated cAMP production in vitro: a possible mechanism to explain amiodarone-induced hypothyroidism

“…Gathering all the available data on the effects of AMD such as inhibition of TSH-stimulated cAMP production (5), diminished thyroid hormone secretion (37) and iodine metabolism (38), the effects on peripheral thyroid hormone metabolism (39)(40)(41) and effects on thyroid hormone receptors (41) may provide a mechanism for the development of hypothyroidism in some patients receiving AMD (3). Additionally the effects of AMD on cell viability are also important.…”

“…In general, the commonest conditions for a failure to 'escape' from an iodine load are immaturity of the thyroid gland, the presence of thyroid autoimmunity or genetic abnormalities of thyroid hormone synthesis. Specifically, in patients with AIH, pre-existing thyroid autoimmunity has been found to be a strong predictor of persistent hypothyroidism (3,4). This failure to autoregulate iodine in states of thyroid autoimmunity may be exacerbated by the increased bioavailability of iodine from AMD.…”

Dificultad en el tratamiento del hipertiroidismo por amiodarona: Presentación de un caso

“…La mayoría permanecen eutiroideos, pero hasta un 15-20% de pacientes desarrollan hipertiroidismo o hipotiroidismo por amiodarona (2). La incidencia de hipotiroidismo varía entre un 1 y 32%, siendo mayor en regiones con alta ingesta de yodo, en mujeres y en pacientes con enfermedad de Hashimoto subyacente y su tratamiento no suele plantear dificultades (4).…”