Use of lithium in the treatment of thyrotoxicosis.

OBJECTIVES: To evaluate the efficacy and safety of lithium in the treatment of thyrotoxicosis, and to study the dose and serum levels at which therapeutic response occurs. DESIGN: Retrospective study. SETTING: Thyroid clinic of a regional hospital in Hong Kong. PATIENTS: Thirteen patients with thyrotoxicosis pending therapy with radioiodine or surgery, in whom thionamides were contra-indicated due to adverse reactions or failure of treatment. MAIN OUTCOME MEASURES: Free thyroxine levels, time to euthyroidism, and side-effects of lithium. RESULTS: A satisfactory response, defined as a fall by 40% or more in free thyroxine levels and clinical improvement, was achieved in eight patients within 1 to 2 weeks of lithium therapy. In four others, response occurred in 3 to 5 weeks. Response was slow and inadequate in one patient due to 'escape'. The median dosage of lithium was 750 mg daily, with a range of 500 to 1500 mg daily. The median serum lithium level was 0.63 mmol/L. Lithium toxicity was observed in one patient. CONCLUSIONS: A relatively low dose of lithium offers a safe and effective alternative means of controlling thyrotoxicosis in patients who cannot tolerate or do not respond to thionamides.