Fig. 1-15. Schematic of the known regulatory elements of thyroglobulin, thyroperoxidase, sodium/iodide symporter and TSH receptor genes. The organization of the proximal promoter and upstream enhancer elements of the different genes is depicted as determined in the species studied so far. Coordinates of the proximal promoters are in base pairs and refer to the transcription start site as +1. The positions of the upstream enhancer elements relative to the transcription start site are not indicated as they vary extensively among the different species.