Rise and fall of thyroid radiologic density during the time course of amiodarone-induced thyrotoxicosis

Abstract

Background and Objective It has been reported recently in a cross sectional study that patients with amiodarone induced thyrotoxicosis (AIT) showed a ‘white’ thyroid on unenhanced computed tomography, due to intrathyroid iodine accumulation. However, the link between increase in thyroid radiologic density and amiodarone induced thyrotoxicosis remains unknown. We sought to analyze this link. Methods We present the case of a 34-year-old patient with severe sarcoidosis-related hypertrophic cardiomyopathy who was followed with successive unenhanced CT scans integrated with FDG PET scans. After the first CT scans the patient, who initially had a normal thyroid function, was exposed to amiodarone during 23 months and developed AIT, very likely by thyroiditis (AIT type 2). There were no thyroid antibodies, no evidence of thyroid sarcoidosis on FDG PET scan, while thyroid sonogram showed a homogenous 22 ml moderate goiter with normal echogenicity and no nodules. Results Analysis of the successive enhanced CT scans revealed that after initiation of amiodarone treatment, thyroid radiologic density steadily increased before detection of AIT, peaked after cessation of amiodarone and initiation of thyrotoxicosis treatment, before returning to normal as thyrotoxicosis receded. Thyroid volume also showed a moderate increase, peaking at the detection of thyrotoxicosis, before returning to normal. Conclusion This case suggests that AIT is preceded by a very high intrathyroid iodine accumulation before the ‘burst’ of thyroiditis occurs and that measurements of thyroid gland radiological density might predict the development and remission of AIT.

Short review: novel concepts in the approach to patients with amiodarone-induced thyrotoxicosis

“…In details, the authors reported the incidental finding in an AIT2 patient of a “white thyroid” resembling a thyroid image on an enhanced CT scan; a subsequent comparison between thyroid densities (measured in Hounsfield units) of AIT2 patients compared to either patients with no thyroid dysfunction under amiodarone treatment or to healthy controls revealed a significant decrease when moving from the former to the latter [ 26 ]. This study was further supported by a report of a single patient who underwent several CT scans before and along the course of AIT2: as a matter of fact, thyroid density increased after amiodarone administration and before detection of AIT, peaked after initiation of treatment for thyrotoxicosis, and returned to normal when thyrotoxicosis remitted [ 27 ]. Being the observation of the “white thyroid” subsequent to the publication of the most recent guidelines [ 9 , 10 ], this diagnostic tool is currently not included in the AIT workup.…”

Relationship between Thyroid CT Density, Volume, and Future TSH Elevation: A 5-Year Follow-Up Study

“…Accordingly, iodine-rich intake may result in increased thyroid CT densities prior to the onset of the aforementioned conditions. Although comprehensive studies on the relationship between dietary iodine exposure and thyroid CT densities are lacking, it is known that excessive iodine exposure through medications like amiodarone can lead to an increase in thyroid densities [16,17]. Additionally, there are scarce longitudinal data regarding thyroid volume.…”