Coexistent presentation of Graves' disease and an autonomous thyroid nodule following administration of an iodinated contrast load

Objective: Exposure to a high iodine load increases the risk of iodine-induced thyroid dysfunction in vulnerable populations, including the elderly. We report a case of an elderly patient who presented with coexisting Graves' disease and a potential autonomously-functioning thyroid nodule following administration of iodinated contrast. Methods: Clinical, laboratory, and radiographic data are presented. Results: A 70-year-old man had a history of subclinical hyperthyroidism following an iodinated computed tomography (CT) scan study four years prior. He presented to the Endocrine Clinic with a new diagnosis of hyperthyroidism 20 weeks after a iodinated contrast CT. A thyroid uptake and scan revealed increased uptake in the right lower lobe (confirmed as a nodule by ultrasound), and diffusely increased uptake bilaterally, findings consistent with both Graves' disease and a superimposed autonomous thyroid nodule. One year later, without treatment, the patient's serum thyroid function and thyroid uptakes had normalized, presumed to result from remission of the Graves' disease and resolution of the thyroid nodule's autonomy. Conclusion: This case demonstrates the co-occurrence of Graves' disease and a functional thyroid nodule. The nodule did not continue to retain autonomy following remission of the Graves' disease. The exposure to iodinated contrast may play a role in the mechanism of its onset and remission. Keywords: Hyperthyroidism, Marine-Lenhart syndrome, Iodinated contrast, Iodine, Subclinical hyperthyroidis