Drug-Induced Thyroid Toxicity

The thyroid is a highly specialized endocrine organ devoted to the production of thyroid hormone, via organification of inorganic iodine. To accomplish this task, the thyroid follicular cell employs a rather complex of unique enzymes, transporters and regulatory factors. Both a classical endocrine feedback mechanism and less understood intracellular mechanisms maintain a constant output of thyroid hormone in normal physiology. Such a complex system can be altered by a number of pharmacological interferences. These interferences can be grouped under two broad categories: direct toxic effects on the thyroid gland, and immune mediated effects precipitated by immune modulators. Drug effects on the thyroid have been studied for several decades thanks to the availability of accurate methods for assessing thyroid physiology. The effects of some of these drugs, such as amiodarone and lithium have been known for many years, but novel antineoplastic agents introduced more recently have been the focus of intense attention over the past few years. This chapter concisely summarizes our current knowledge on drugs capable of altering thyroid function or structure, with attention to underlying mechanisms.

Keywords: Alemtuzumab, amiodarone, endocrine disruption, drugs, interferon- α, interferon-β, interlekin-2, lithium, thyroid gland, toxicity, tyrosine kinase inhibitors.