AMIODARONE-INDUCED AND IODINE-INDUCED THY ROTOXICOSIS - HISTOLOGICAL,IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL OBSERVATIONS

Amiodarone is a widely-used anti-arythmic drug that induces an iodine overload and, in 1 to 23 % of the patients, a thyrotoxicosis. In a few cases, the thyrotoxicosis may be refractory to conventional pharmacol ogical therapy, thus leading to thyroidectomy. We report the thyroid g land pathology in 5 thyroidectomies that were performed for uncontroll ed thyrotoxicosis, induced by amiodarone (4 cases) and by Colchimax(R) , another iodine-rich drug (1 case). Two cases have been studied by el ectron microscopy. Pathologic findings were : [1] colloid transformati on of the parenchyma, [2] areas of follicular disruption with numerous foamy macrophages in the colloid, [3] regenerative areas and [4] a mo derate T lymphocytic infiltration. No lysosomal lamellar inclusion bod y was found by electron microscopy. These lesions may be rather specif ic of an iodine toxicity. The pathogeny is still misunderstood, and pr obably complex. It may essentially involve toxic mechanisms, as well a s immunologic or allergic mechanisms.