A strong solution: Lugol’s iodine for long-term Graves’ control after carbimazole toxicity — ASN Events
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A strong solution: Lugol’s iodine for long-term Graves’ control after carbimazole toxicity (#311)

Lucy Birtwistle 1 , Matti Gild 1 2 , Lyndal Tacon 1 2
  1. Endocrinology, Royal North Shore Hospital, St Leonards, NSW, Australia
  2. Sydney Medical School, Faculty of Medicine and Health Sciences, University of Sydney, Sydney, NSW, Australia

A previously independent 78-year-old woman presented with rapid atrial fibrillation and newly diagnosed thyrotoxicosis (TSH <0.02 mIU/L, fT3 24 pmol/L, fT4 65 pmol/L, TRAb 1.0 IU/L). Tc-99m thyroid uptake scan was consistent with Graves’ disease. She commenced carbimazole 10 mg BD, metoprolol, and apixaban. Twenty days later, she re-presented with fever, anorexia, and profound neutropenia secondary to carbimazole-induced agranulocytosis.

Her hospitalisation lasted 5 months, including 6 weeks in intensive care for multiorgan failure. She developed neutropenic polymicrobial sepsis from Streptococcus pyogenes, Serratia marcescens, and Candida tropicalis. Management included granulocyte colony-stimulating factor, intravenous immunoglobulin, antimicrobials, vasopressor support, and renal replacement therapy. Major complications included recurrent thromboembolic strokes, with anticoagulation repeatedly interrupted due to haematoma and thrombocytopenia. She also developed critical illness myopathy, immobilisation hypercalcaemia, malnutrition requiring gastrostomy feeding, and profound functional decline necessitating discharge to residential aged care.

Carbimazole was ceased on admission. Thyrotoxicosis was initially controlled with glucocorticoids, and iodine administered through multiple contrast-enhanced CT imaging across 3 months. Lugol’s solution (5% elemental iodine, 10% potassium iodide) was later initiated on day 100 at 0.5 ml BD. Thyroidectomy was considered but deferred due to haemodynamic instability, development of recurrent thromboembolic strokes and eventual frailty. Lugol’s iodine at 0.5 ml BD has been continued for five months post-discharge, maintaining subclinical hyperthyroidism (TSH 0.01 mIU/L, fT3 4.4 pmol/L, fT4 17.1 pmol/L, TRAb 0.9 IU/L), along with metoprolol and denosumab.

Antithyroid drug-induced agranulocytosis is a rare but life-threatening complication of thionamide therapy that precludes further use of this drug class. Definitive treatment of thyrotoxic state with thyroidectomy or radioactive iodine may not be feasible due to comorbidities, operative risk or practical challenges. In such circumstances, prolonged Lugol’s solution may provide an effective alternative for controlling thyrotoxicosis,1,2 as demonstrated in this case. Evidence supporting its long-term use outside the perioperative settings remains limited.3

  1. Watanabe N. A narrative review of long-term inorganic iodine monotherapy for Graves' disease with a historical relationship between iodine and thyroid. Endocr J 2025; 72(1): 23–36.
  2. Magvanjav O, MacLeod RS, Balasubramanian P, et al. Iodine for the Outpatient Management of Graves' Disease: A Case Series of 7 Patients. AACE Endocrinol Diabetes 2026; 13(1): 83–87.
  3. Ross DS, Burch HB, Cooper DS, et al. 2016 American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis. Thyroid 2016; 26(10): 1343–1421.