Iopanoic acid rapidly restores euthyroidism in refractory thyrotoxicosis pre-thyroidectomy: a retrospective study

Objective Restoration of euthyroidism in patients with thyrotoxicosis prior to thyroidectomy is recommended to decrease perioperative morbidity and thyroid storm risk. This is challenging when conventional anti-thyroid medication is contraindicated or ineffective. Iopanoic acid (IOPA), an iodinated contrast medium formerly used as an oral cholecystographic agent, may facilitate treatment of thyrotoxicosis, but limited manufacture precludes its use in the UK. We investigated the effectiveness and safety of IOPA for optimizing thyroid status in treatment-resistant thyrotoxicosis prior to thyroidectomy at a referral centre.

Methods With prior permission of our Drug & Therapeutics Committee, we sourced laboratory-grade (>98% pure) IOPA and administered this orally to control ongoing, severe, thyrotoxicosis prior to thyroidectomy in 12 patients with inadequate response to standard therapies. Underlying aetiologies included Graves' disease, amiodarone-induced thyrotoxicosis, toxic multinodular goitre and Resistance to Thyroid Hormone beta. Medical case notes were reviewed retrospectively to analyse clinical and biochemical outcomes.

Results All patients exhibited a decline and normalization / near-normalization of free T3 (FT3) levels (mean 55% decrease, SEM 4.5%), with minimal changes in FT4 levels. Eleven patients proceeded to uneventful thyroidectomy and IOPA was well-tolerated with no directly attributable side-effects.

Conclusions IOPA is a safe and effective agent for controlling biochemical thyrotoxicosis in preparation for thyroidectomy, including disease refractory to conventional medication. Highly pure, laboratory-grade iopanoic acid that is approved for human use, is now available in the UK; consideration should be given to more wide-spread use for emergency treatment of life-threatening hyperthyroidism.