TH and Allan-Herndon-Dudley syndrome: Consistent with these preclinical observations, patients with TH deficiency in the CNS due to mutations in the TH transporter MCT8 (Alan-Herndon-Dudley-Syndrome, AHDS) exhibit delayed cortical and cerebellar development and myelination, loss of parvalbumin expression, abnormal calbindin-D28k content and impaired axonal maturation [42–45].