Endocrine Abstracts

Objective: Preoperative iodine therapy due to toxic nodular goiter (TNG) is discouraged as iodine may cause an aggravation of hyperthyroidism. In Graves’ disease iodine has been used for a century but little data is available on iodine treatment in TNG. We aimed to examine if a short course of iodine treatment is safe to administer in TNG.

Method: 20 patients with TNG with persistent subclinical to mild hyperthyroidism were included at our tertiary care center of Endocrinology. This was a non-randomized open label intervention without controls. All participants were treated with Lugol’s solution 5 % (Potassium Iodide) 3 drops thrice daily p.o. for ten days, in total 603 mg iodine. Heart rate, TSH, free T4 (fT4) and free T3 (fT3) concentrations before (day 0) and after treatment (day 10) were measured. Thyroid hormone levels were also measured at two time points during the course of treatment to discover possible exacerbation of hyperthyroidism. Heart rate and thyroid hormones before and after treatment were compared using the non-parametric Wilcoxon signed-rank test for paired data. Any possible adverse reaction was reported.

Results: Median age was 63.5 years, interquartile range (IQR) 56 – 68. Female to male ratio 19:1. Peripheral hormone levels decreased and TSH levels increased. Differences in TSH, fT4, fT3 levels were statistically significant. The difference in heart rate was not statistically significant. No exacerbations of hormone levels were noticed in any of the participants during treatment. Six participants (30 %) reported symptoms related or possibly related to treatment (gastrointestinal symptoms, headache). All symptoms were classified as mild and temporary. All participants completed the study although one ingested < 80 % of the doses (77%).

Conclusions: In this prospective intervention study on toxic nodular goiter we found that a short course of Lugol’s solution was safe to administer. The reported adverse reactions were mild and temporary. This indicates that Lugol’s solution might be an option for preoperative treatment when antithyroid drugs are not tolerated.