SLC16A2 and Allan-Herndon-Dudley syndrome: Its role in TH transport is crucial for brain TH availability, evidenced by the devastating neurological impairments of Allan-Herndon-Dudley-Syndrome (AHDS) patients with mutations in the MCT8-encoding solute carrier family member 16a2 (Slc16a2) gene on the X-chromosome (Dumitrescu et al. 2004; Friesema et al. 2004).