Background and Objective: The use of amiodarone for the treatment of ventricular and
supraventricular dysrhythmias brings in organism an increased amount of iodine, interfering with
thyroid function. If the treatment needs to be interrupted, iodine remains at abnormal levels for
months or even years. The aim of the study was to review the literature regarding the optimal tests
for early diagnostic and to analyze the role of nuclear medicine tests in the differential and correct
assessment of the amiodarone-induced thyroid pathology.
Methods: We made a review of available publications in PUBMED referring the amiodaroneinduced
thyroid pathology, focusing on the differential diagnosis, made by nuclear medicine tests,
of hypothyroidism (AIH) and hyperthyroidism expressed as: type I amiodarone induced thyrotoxicosis
(AIT I), type II amiodarone induced thyrotoxicosis (AIT II), and less frequently as a mixt
form, type III amiodarone induced thyrotoxicosis (AIT III). We presented cases from the database
of a tertiary center in Cluj-Napoca, Romania.
Results: Despite the frequent complication of thyroid function, this pathology is underestimated
and diagnosed. There is a limited number of studies and clear protocols, especially in the mixed
forms cases. This increase in iodine uptake interferes seriously with thyroid hormone production
and release. The nuclear medicine tests are essential in the correct assessment and differential diagnosis
of different forms of induced thyroid dysfunction. The destruction of the follicular cells
can result in the release of excessive thyroid hormone into the circulation, with potential development
of atrial fibrillation, worsening the cardiac disease, so any benefic therapeutic procedure
should be known; the use of radioiodine as therapy alternative, despite the known limitations induced
by blockade was clear benefic in the case presented. A special attention needs to be addressed
to those patients with differentiated thyroid cancer, which will be submitted to radioiodine
therapy and are under chronic therapy with amiodarone.
Conclusion: The nuclear medicine procedures are essential in the correct assessment and differential
diagnosis of different forms of induced thyroid dysfunction. The radioiodine is not recommended
in AIT, due to stunning effect induced by iodine excess, but in some special, lifethreatening
condition, radioiodine I-131 might be a treatment option.