Utilidad de la gammagrafía tiroidea en el manejo terapéutico del hipertiroidismo inducido por amiodarona

Amiodarone-induced hyperthyroidism is relatively common in iodine-deficient regions. Two types have been described: type I, caused by increased synthesis and release of thyroid hormone in individuals with underlying thyroid disease, can be treated with antithyroid drugs or radioiodine; and type II, a destructive thyroiditis responsive to corticoid therapy but not to antithyroid drugs. It can be difficult to distinguish between the two types, and cases of mixed types have been reported. Objective. to assess the usefulness of thyroid scintigraphy in amiodarone-induced hyperthyroidism. Materials and methods. 27 consecutive patients (13 females) with amiodarone-induced hyperthyroidism. Mean age was 65 years (range: 39-89). All patients underwent 99mTc-pertechnectate thyroid scintigraphy and were classified according to the qualitative estimation of radiotracer uptake: type I (increased / normal uptake): 9 patients, all of whom responded to antithyroid drugs or radioiodine, except one patient with sub-clinical hyperthyroidism who received no therapy; type II (very low or undetectable uptake): 13 patients, 11 of whom responded to discontinuation of amiodarone or prednisone therapy (2 patients). Hyperthyroidism was resistant in 2 patients and required antithyroid drugs or potassium perchlorate; mixed type (low uptake but with underlying thyroid pathology): 5 patients, with variable evolution; all needed antithyroid drugs, one required subtotal thyroidectomy, and another radioiodine treatment. Conclusion. thyroid scintigraphy can establish the correct therapeutic approach in most cases of amiodarone-induced hyperthyroidism, making it essential in the clinical management of these patients.