Effects of thyroglobulin and pendrin on iodide flux through the thyrocyte.

Iodide transport by thyrocytes involves porters on the apical and basal surfaces of the cell facing the follicular lumen and bloodstream, respectively. Recent work identifies pendrin as an apical porter and shows that follicular thyroglobulin is a transcriptional regulator of the gene encoding pendrin and other thyroid-restricted genes. For example, whereas follicular thyroglobulin suppresses the gene expression and activity of the sodium iodide symporter (NIS), it increases pendrin gene expression. A potential new dynamic for iodide flux and thyroid hormone formation in thyrocytes has thus emerged and is supported by in vivo data.