Endocrine Abstracts

Introduction: A significant number of patients are intolerant of anti-thyroid drugs (ATD) and thyroidectomy remains the only treatment option available to patients who decline radioiodine as definitive therapy. As patients with poorly controlled thyrotoxicosis are at risk of developing thyroid storm, optimal pre-operative control of hyperthyroidism is essential. Rapid thyroid blockade (RTB) with the contrast agents sodium ipodate and iopanoic acid were attractive treatment options but these agents are no longer available for routine use.

Aims: To explore the safety and efficacy of rapid thyroid blockade with Lugol’s iodine in the pre-surgical management of Graves’ thyrotoxicosis.

Method: Lugol’s iodine (0.2 ml three times a day) was administered to six patients with Graves’ thyrotoxicosis who were resistant to treatment with the conventional ATD, carbimazole, and propylthiouracil. Treatment was started 10 days prior to planned thyroid surgery. TSH at baseline and subsequent fT₄ and fT₃ were measured at fixed intervals prior to thyroidectomy.

Results: All patients were female; mean (S.D.) pre-treatment fT₄ and fT₃ levels were 30.1 pmol/l (8.12) and 8.8 pmol/l (5.9) respectively. Mean nadir fT₄ and fT₃ levels after treatment were 16.2 and 4.4 pmol/l respectively. Mean percentage fT₄ reduction was 45.2% and mean percentage fT₃ reduction was 40.4%. fT₄ and fT₃ dropped at an average rate of 7.6 pmol/l per day. Mean absolute reductions in fT₄ and fT₃ levels were13.9 and 4.4 pmol/l respectively. All patients were biochemically euthyroid preoperatively. The mean time to normalise fT₄ was 3.8 days (S.D. 1.72). On patient experienced transient adverse effects with Lugol’s iodine.

Conclusion: In this pilot study, Lugol’s iodine was effective in rendering patients biochemically euthyroid prior to planned thyroidectomy. The long-term safety and efficacy of crash thyroid blockade with Lugol’s iodine needs to be assessed in a larger cohort of patients.