Chapter 96 - Influence of Iodine-Containing Pharmaceuticals on Iodine Status and Thyroid Function: Iodine-Induced Hyperthyroidism and Hypothyroidism

Abstract

A high dose of iodine can cause iodine-induced thyroid dysfunction in susceptible individuals, especially in patients with underlying thyroid disease, fetuses, and neonates. Development of iodine-induced thyroid dysfunction is influenced by prior iodine status, and such thyroid dysfunction is prevalent in iodine-deficient areas. Iodine-containing pharmaceuticals, such as povidone-iodine (PVP-I), radiographic contrast media and amiodarone, are a major cause of iodine overload. Among the types of thyroid dysfunction induced by iodine-containing pharmaceuticals, hypothyroidism in the fetus or neonate and amiodarone-induced thyrotoxicosis are severe problems. Long-term treatment with PVP-I, even at relatively low doses, can also lead to thyroid dysfunction. Amiodarone has intrinsic effects on the thyroid gland and thyroid hormone production, in addition to those related to an excessive iodine load and it induces dysfunction more frequently than any other iodine-containing pharmaceutical. Iodine-induced hyperthyroidism, especially thyrotoxicosis caused by amiodarone, is often difficult to treat, whereas iodine-induced hypothyroidism usually resolves after iodine withdrawal. Individuals at risk of developing iodine-induced thyroid dysfunction should be observed carefully if they are administered iodine-containing drugs.