Thyroid Graphic (IMAGE) Kansas State University Caption In addition to actively extracting I-, or iodide, from the circulation, thyroid follicular epithelial cells must also translocate I- into a central intrafollicular compartment, where it combines with thyroglobulin to form thyroid hormone precursor. Credit Peying Fong Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.