SLC16A2 and Allan-Herndon-Dudley syndrome: Two animal models of MCT8 deficiency have been generated recently, the mct8−/− mouse53 and a transgenic zebrafish.54 The mct8−/− mouse accurately replicates the human thyroid profile,55,56 but does not show any of the neurological features seen in patients with AHDS, suggesting the presence of additional thyroid hormone transporters with a synergistic effect in the mouse brain.