SUN-353 Iodine Solution for Treatment of Graves Hyperthyroidism Complicated by Acute Liver Injury

Abstract Disclosure: S. Puri: None. T.S. Tylee: Abbvie. Background: Liver dysfunction is commonly seen in hyperthyroidism. In Graves’ Disease (GD), this may be due to TSH-receptor antibodies (TRAb) causing inflammatory injury to hepatocytes. In addition, anti-thyroid drugs, such as methimazole (MMI) are known to cause liver damage. For patients with GD who have evidence of liver dysfunction while on MMI, it can be difficult to determine if the cause is the hyperthyroidism itself, or complications from MMI treatment. It is unclear how best to manage these patients. Here we describe a case of GD complicated by acute liver injury while on MMI who was successfully managed with potassium iodine (KI). This may be a safe alternative to treating hyperthyroidism in the setting of liver dysfunction. Clinical Case: A 37-year-old otherwise healthy female presented with hyperthyroid symptoms, and new transaminitis (AST 47, ALT 82). Thyroid labs were consistent with GD (TSH <0.003, FT4 4.2, TRAb 8.00). She was started on MMI 20 mg daily. TFTs showed minimal improvement after 1 month (FT4 3.1), transaminitis worsened (AST 88, ALT 149) and hyperthyroid symptoms persisted. MMI was discontinued due to worsening LFTs and KI was started (2% solution, 15 drops TID for 10 days). Her hyperthyroid symptoms quickly resolved, T4 levels normalized within one week (TSH 0.003, FT4 1.0) with improvement in LFTs (AST 38, ALT 59). MMI was then re-introduced at 5 mg daily. LFTs remained stable on MMI and hyperthyroidism resolved. Clinical Lessons: When transaminitis is present in the setting of GD with MMI treatment, it is difficult to determine if the liver injury is due to thyrotoxicosis or MMI toxicity. In this case, the patient did have transaminitis prior to initiating therapy, but this worsened with the addition of MMI further complicating the picture. Her hyperthyroidism persisted, but given the worsening LFTs, it was not felt further up titration of MMI would be safe. Iodine is used in cases of thyroid storm to acutely block thyroid hormone production and release through the Wolff-Chaikoff effect. This case depicts a novel approach of using KI in the outpatient setting to quickly address thyrotoxicosis in a patient with liver injury in which MMI is contraindicated. The rapid improvement in LFTs with resolution of hyperthyroidism, suggested transaminitis was most likely due the hyperthyroidism and MMI was safely resumed at lower doses. This approach is applicable to patients with symptomatic hyperthyroidism and concurrent liver injury who are not candidates for RAI or thyroidectomy. Presentation: Sunday, July 13, 2025