P-120 A RARE PRESENTATION OF HYPERTHYROIDISM IN THE GASTROENTEROLOGY INPATIENT CLINIC

Abstract Introduction Chronic exogenous exposures related to perianal fistula care may lead to systemic effects in patients with Crohn’s disease and require a multisystemic evaluation. In this case, we aimed to raise awareness by presenting a rarely encountered treatment-related complication in a patient with Crohn’s disease Clinical Case A 22year-old female with history of ileocolonic, fistulizing Crohn’s disease had previously undergone right hemicolectomy and enterovesical fistula repair. The patient, who had prior exposure to adalimumab and ustekinumab, was most recently on upadacitinib, which had been discontinued 2 months earlier due to the development of a perianal fistula under treatment. Because of recurrent perianal fistulas, she had been under follow-up by general surgery. She was admitted to the gastroenterology clinic for further evaluation due to anal pain and elevated acute phase reactants. On admission, physical examination revealed complaints of hot flashes, sweating, and hand tremors. Tenderness in the perianal region and an active fistula tract were observed. Laboratory tests showed CRP 124 mg/L, TSH 30.80 pmol/L, and fT4 >154.80 pmol/L. Thyroid ultrasonography(USG) was normal, while Tc-99m pertechnetate uptake was measured at 0.15% with a scintigraphic pattern reported as “compatible with exogenous iodine exposure/thyroiditis.” Thyroid antibody profile was negative. Spot urine iodine was 57 µg/L. Upon re-evaluating the history, it was learned that the fistula tract had been irrigated regularly with povidone-iodine for the past three months. With elevated urinary iodine levels and regular povidone-iodine exposure, the patient was diagnosed with iodine-induced thyrotoxicosis. Endocrinology consultation recommended initiation of methimazole 30 mg/day and propranolol 20 mg twice daily, with beta-blocker dose titrated according to symptoms. The patient was monitored daily for thyroid storm.Corticosteroid therapy was not initiated due to the presence of active perianal fistula and abscess. During this period, infection control was achieved with parenteral antibiotics, surgical drainage and seton placement, as well as initiation of infliximab therapy. The patient achieved control of the perianal infection, and Infliximab treatment was given for Crohn's. With antithyroid and symptomatic treatment, thyrotoxic manifestations were stabilized. Conclusion This case demonstrates that chronic exogenous iodine exposure during perianal fistula care in Crohn’s disease may lead to systemic thyroid dysfunction. In the literature, iodine toxicity has been reported to cause various thyroid disorders. For the diagnosis; thyroid function tests, spot urinary iodine measurement, and thyroid scintigraphy are of particular importance. In conclusion, systemic effects of iodine-containing antiseptics used during perianal fistula care in Crohn’s patients should be carefully considered, and thyroid functions should be monitored regularlyTable 1:Follow-up of the patient's thyroid function test results