Abstract
Background: Thyrotoxicosis can be mistaken for conditions such as atrial fibrillation and pulmonary embolism (PE) given the nonspecific symptoms of fatigue, palpitations, and dyspnea. Patients often undergo further imaging on presentation to the emergency room (ER), many of which use iodine for contrast. This can put patients at increased risk for iodine induced hyperthyroidism and delay definitive treatment in patients with Graves’ disease, the most common cause of hyperthyroidism.
Clinical Case: A 53-year-old male with history of hyperthyroidism, atrial fibrillation, and prior PE presented with palpitations to the ER. He developed worsening dyspnea on exertion and palpitations over the last three days. He was unable to afford his medications, including methimazole, for the last nine months. In the ER he was in atrial fibrillation with rapid ventricular response. Due to concern for PE, he underwent a CTA with contrast, which was negative. His physical exam was notable for a diffusely enlarged goiter. His labs showed low TSH <0.01 (norm 0.35-5.50mIU/L) and high free T4 >7.77 (norm 0.9-1.8ng/dL). TSH stimulating antibodies were elevated at 1.9 (norm <1.3 TSI index), consistent with Graves’ hyperthyroidism. Endocrinology was then consulted for severe thyrotoxicosis, initially treating the patient with PTU and propranolol. The patient was transitioned to methimazole and continued propranolol on discharge. Since he was given contrast, plan was for repeat thyroid uptake scan and iodine ablation in 3 months. However, patient was not compliant with medications, resulting in readmission for thyrotoxicosis 3 months later.
Conclusion: This case highlights the impact of increased use of contrast in imaging in hyperthyroid patients. Hyperthyroid patients are at an increased risk for emboli. However, iodine can cause contrast-induced hyperthyroidism and delay definitive treatment of Graves’ disease. As almost half of thyrotoxic patients receive iodinated contrast prior to an endocrine consultation, endocrinologists should work with emergency physicians to develop a set of guidelines to identify at risk populations for hyperthyroidism (1). We advocate for urgent thyroid testing in patients with new onset atrial fibrillation, a history of Graves’ disease, specific symptoms of Graves’, or those taking thyrotoxic-inducing medications. This will assist in determining if patients should receive a prophylactic dose of anti-thyroid medication prior to iodinated contrast imaging. These guidelines can help prevent contrast induced hyperthyroidism and disruptions in treatment of Graves’ while still imaging patients for other diagnoses on the differential.
Reference: (1) Giacomini A, et al. Urgent thyroid-stimulating hormone testing in emergency medicine: A useful tool? J Emerg Med. 2015;49(4):481-487.
Urinary Iodine Excretion and Serum Thyroid Function in Adults After Iodinated Contrast Administration
