Background: In 1924 a case series was reported about the efficacy of high dose iodine to suppress to establish euthyroidism prior to thyroidectomy for Grave’s disease. After the discovery of anti-thyroid drugs (ATD) this approach gradually disappeared from clinical practice.

Objectives: To re-examine the efficacy of high dose iodine therapy to achieve euthyroidism rapidly, prior to surgery

Methods: Retrospective analysis of patients treated with high dose potassium iodine for hyperthyroidism due to Graves’ disease, not tolerating ATD treatment because of side effects.

Results: From January 2015 to May 2018, 14 patients (3 men, 11 women) were admitted for treatment with potassium iodine 250 mg tid, for 7 – 12 days. Age ranged from 23 to 76 years, and body weight from 50 to 108 kg. In all patients, Grave’s disease was confirmed by the presence of anti-TSH receptor antibodies. ATD was discontinued because of agranulocytosis (3), allergic skin reactions (3), gastrointestinal side effects (3), hyperthyroidism not responding to high dose ATD (3), and other reasons (2). Potassium iodine was administered for 8.6 ± 0.7 days and decreased plasma FT4 levels from 48.5 ± 3.8 to 16.4 ± 1.7 pmol/l (mean ± SE), and FT3 from 19.0 ± 3.3 to 6.1 ± 0.4 pmol/l. At the day of surgery FT4 was within the normal range in all but one patient, and FT3 levels were still slightly elevated in 2 patients. Iodine treatment was not associated with side effects.

Conclusions: High dose potassium iodine treatment remains a safe and effective approach to achieve euthyroidism rapidly, prior to thyroidectomy for Graves’ disease. It is still very useful as last resort treatment.