Unusual scintigraphic finding in a patient with amiodarone - induced thyrotoxicosis : a case report
Journal
Journal of Morphological Sciences
Date Issued
2021
Author(s)
Abstract
Amiodarone, an antiarrhythmic drug with 37% iodine of its weight, is often used for treatment of
severe cardiac arrhythmias. Enormous iodine content and structural similarity to
thyroxine leads to thyroid
dysfunction in 14
-
18% of patients.
A 64
-
year
-
old man presented at our department with signs of thyrotoxicosis for further work up.
He reported taking amiodarone for treatment of atrial fibrillation for two years. The patient deni
ed any
thyroid dysfunctions in the past. Full thyroid examination revealed elevated FT4 and suppressed TSH, with
undetectable level of thyroid antibodies, increased iodine urinary concentration and normal thyroid
ultrasound features. Although the above men
tioned was indicative for amiodarone
-
induced thyrotoxicosis
(AIT) type 2, 99mTc
-
pertechnetate scan showed normal thyroid uptake, highly unusual for iodine
contamination and destructive thyroiditis. We presumed that this was a mixed form of AIT. Amiodarone
administration was stopped and the patient was put on antithyroid drug therapy with thiamazole. During
the follow up period he became clinically and biochemically euthyroid and thiamazole was discontinued.
Thyroid screening should be performed in all patie
nts undergoing amiodarone treatment. The
presented case highlights the challenge of differentiation and management of a form of AIT with mixed
features of both types.
severe cardiac arrhythmias. Enormous iodine content and structural similarity to
thyroxine leads to thyroid
dysfunction in 14
-
18% of patients.
A 64
-
year
-
old man presented at our department with signs of thyrotoxicosis for further work up.
He reported taking amiodarone for treatment of atrial fibrillation for two years. The patient deni
ed any
thyroid dysfunctions in the past. Full thyroid examination revealed elevated FT4 and suppressed TSH, with
undetectable level of thyroid antibodies, increased iodine urinary concentration and normal thyroid
ultrasound features. Although the above men
tioned was indicative for amiodarone
-
induced thyrotoxicosis
(AIT) type 2, 99mTc
-
pertechnetate scan showed normal thyroid uptake, highly unusual for iodine
contamination and destructive thyroiditis. We presumed that this was a mixed form of AIT. Amiodarone
administration was stopped and the patient was put on antithyroid drug therapy with thiamazole. During
the follow up period he became clinically and biochemically euthyroid and thiamazole was discontinued.
Thyroid screening should be performed in all patie
nts undergoing amiodarone treatment. The
presented case highlights the challenge of differentiation and management of a form of AIT with mixed
features of both types.