Development and Standardization of an Assay to Evaluate the <i>In Vitro</i> Inhibition of Thyroid Peroxidase -Catalyzed Iodination Using FTC-238-hrTPO Cell Homogenates

Introduction: A proper thyroid hormone homeostasis plays a crucial role in the human development and basal metabolic rate and disruption of thyroid hormone homeostasis may lead to severe neurodevelopmental and physical adverse effects. To improve identification of thyroid hormone system disruptors, the validation of multiple fast, low-cost, robust, sensitive, animal-free, and human-relevant thyroid in vitro assays was coordinated by the European Union Reference Laboratory for alternatives to animal testing. The thyroid peroxidase (TPO) enzyme plays a critical role in the thyroid hormone synthesis and is a potential target of xenobiotics. In this study, the development and in house validation of an in vitro assay for evaluation of chemicals for the potential interference with TPO-catalyzed iodination is reported.