7786 Successful Use of Lithium in Hyperthyroidism Following a Carbimazole-Induced Agranulocytosis: A Case Report

Abstract Disclosure: J.G. Sazon: None. D.V. Bawal: None. J.V. Chua: None. J. Reyes: None. Graves' disease (GD) constitutes a significant proportion of global thyrotoxicosis cases. Carbimazole is an ATD with a notably and a rare yet severe complication of ATD with substantial adverse implications for health, is agranulocytosis. This condition is reversible if recognized early and treated accordingly. We report a case of successful use of lithium prior to radioiodine ablation (RAI) in management of thyrotoxicosis in the context of Carbimazole-induced agranulocytosis. This is a case of a 38-year-old female newly-diagnosed with Graves' Disease presenting with palpitations. Diagnostics showed FT4 >100 (11.9 – 21.6 pmol/L), TSH at <0.005 (0.270 – 4.200 mIU/L) and positive TSH receptor antibodies (TRAb) at 13.9 IU/L (normal value: <1.76 IU/L). Electrocardiogram revealed Atrial Fibrillation. She was initiated on Carbimazole 30 mg/tab OD, Apixaban 10 mg/tab OD, and Bisoprolol 10mg/tab OD. After 28 days of drug-intake, she developed fever (TMax 38.5°C) and work-up revealed severe neutropenia with an ANC of 0. Peripheral blood smear showed agranulocytosis. A seven-day course of piperacillin-tazobactam and moxifloxacin was administered, along with G-CSF at a dose of 300ug BID. Subsequently, was scheduled for Radioactive Iodine (RAI) therapy for definitive treatment. In the interim, with persistent tachycardia and elevated thyroid function tests (FT3 22.20 pmol/L, FT4 47.24 pmol/L) Lithium 450mg/tab BID and Prednisone 40mg/day was initiated, providing significant relief from hyperthyroid symptoms. RAI was administered with a dose of 24mci. Ten days post-RAI, thyroid hormone levels further improved. Four weeks after RAI, repeat tests revealed hypothyroidism. Levothyroxine was initiated at 12.5 mcg and gradually adjusted. Pre-RAI administration of lithium serves to mitigate alterations in serum thyroid hormone concentrations and augments the efficacy of RAI therapy. In this study, the utilization of lithium aimed to regulate thyrotoxicosis and preemptively curtail the elevation of FT4 levels. Lithium emerges as a particularly suitable therapeutic option for patients experiencing adverse effects related to ATDs prior to undergoing definitive therapies such as RAI or thyroidectomy. Furthermore, imperative to the prevention of agranulocytosis, an enhanced understanding of its deleterious effects through patient education is deemed vital. Presentation: 6/2/2024