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Impaired Iodide Organification in Autonomous Thyroid Nodules

Departments of Nuclear Medicine (R.M.-R., B.-N.-T.T., S.G.) and Endocrinology (B.C.), Hôpital Erasme, Université Libre de Bruxelles, 1070 Brussels, Belgium; Experimental Medical Imaging (A.S.), Department of Physics, Université de Liège, 4000 Liège, Belgium; and Department of Endocrinology (C.D.), Université Catholique de Louvain, 1200 Brussels, Belgium

Address all correspondence and requests for reprints to: Rodrigo Moreno-Reyes, Hopital Erasme, Université Libre de Bruxelles, route de Lennik 808, 1070 Brussels, Belgium. E-mail: rmorenor{at}ulb.ac.be.

Context: The clinical evolution of autonomous thyroid nodules (ATN) is unpredictable, and thyrotoxicosis is observed at variable nodule size. In vitro data suggest that hydrogen peroxide production is decreased in ATN, indicating intranodular iodide organification impairment.

Objective: We aimed to determine iodide organification efficiency in ATN and its relationship with thyroid status in patients.

Design: Forty-six patients with a single ATN on the ¹²³I thyroid scan were included in the study. Biological evaluation and iodine perchlorate (I-ClO₄) discharge test were carried out in all subjects.

Setting: The study took place at an academic hospital.

Results: Among the 46 patients, 28 patients (61%) had a positive I-ClO₄ discharge test with a mean ± SD value of discharge of 42 ± 13%, and 18 (39%) had a negative discharge test with mean ± SD of 5 ± 9%. In the group of patients with a negative discharge test but not in the group with a positive test, serum-free T₃ and free T₄ concentrations were significantly correlated with the ¹²³I uptake. The severity of hyperthyroidism was not different between both groups.

Conclusions: Intranodular iodide organification was impaired in most patients with ATN. Whether differences in organification capability could predict the risk for evolution to overt hyperthyroidism in patients with ATN remains to be established.