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.

Key words: Graves' disease; Lithium; Thyrotoxicosis; Thyroxine

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