Endocrine Abstracts

Background and aim: There is an increasing use of computed tomography (CT) scans with an iodine-based contrast medium. Last year, a large University Hospital in Denmark performed 50 000 CT scans where each injection contained between 3500 and 7000 μg free iodine corresponding to 23–45 times normal daily intake. We wished to investigate if patients with newly diagnosed hyperthyroidism had been exposed to an iodine based CT scan within 1 year prior to symptoms of hyperthyroidism.

Materials and methods: All patients with newly diagnosed hyperthyroidism (either first time episode or recurrent) through 1 year (2010) were linked individually with a register for CT scans performed in 2009 and 2010. Only cases where a CT scan was performed prior to an outbreak of hyperthyroidism were included.

Results: 230 new cases of hyperthyroidism were originally classified as: 101 patients with Graves’ disease (73 new, 28 with recurrent), 72 with multinodular goitre, 9 with amiodarone or iodine-induced hyperthyroidism, 8 with HCG-induced hyperthyroidism, 26 with subacute thyroiditis, 11 with postpartum thyroiditis, 1 with painless thyroiditis, 1 was Ipilimumab-induced, and finally 1 induced by Interferon. Fourteen patients, corresponding to 0.0003% of all contrast injections, but 6.1% of all patients with hyperthyroidism, had undergone a CT scan before the outbreak of hyperthyroidism. Based on type of hyperthyroidism, 1/101 (1%) had Graves’ disease, 11/72 (15%) had multinodular goitre and the last two had hyperthyrodism induced by Ipilimumab and Interferon.

Conclusion: From a radiologist’s point of view: a CT scan with iodine-based contrast induces extremely seldom hyperthyroidism. From an endocrinologist’s point of view: a CT scan with iodine-based contrast performed within 1 year prior to symptoms seems significantly associated with outbreak of hyperthyroidism in a multinodular gland (15%) as opposed to Graves’ disease.