title: Clinical phenotype and endocrinological investigations in a patient with a mutation in the MCT8 thyroid hormone transporter.
abstract: Thyroid hormones are known to be essential for growth, development, and metabolism. Recently, the monocarboxylate transporter 8 (MCT8) was identified as a thyroid hormone transporter, and MCT8 mutations have been associated with Allan-Herndon-Dudley syndrome, an X linked condition characterized by severe mental retardation, dysarthria, athetoid movements, muscle hypoplasia, and spastic paraplegia. Here we describe in detail the clinical and biochemical features and the response to thyroid hormone (L-thyroxine (LT4)) administration in a boy with an MCT8 mutation (c.1649delA) that truncates the protein in the twelfth transmembrane domain. It is of note that brain magnetic resonance imaging (MRI) revealed delayed myelination from infancy. Endocrine functions other than thyroid hormone regulation and metabolism were intact, resulting in normal hypothalamic/pituitary function tests. While LT4 administration suppressed thyrotropin (TSH) secretion, no significant changes in thyroid hormone values or clinical symptoms were observed.
  
  
  CONCLUSIONS
  the characteristic thyroid hormone function tests and brain MRI findings may allow screening of high-risk populations for a better understanding of MCT8 pathophysiology.
authors: Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors: Noriyuki
authors: N
authors: Namba
authors: Yuri
authors: Y
authors: Etani
authors: Taichi
authors: T
authors: Kitaoka
authors: Yasuko
authors: Y
authors: Nakamoto
authors: Mariko
authors: M
authors: Nakacho
authors: Kazuhiko
authors: K
authors: Bessho
authors: Yoko
authors: Y
authors: Miyoshi
authors: Sotaro
authors: S
authors: Mushiake
authors: Ikuko
authors: I
authors: Mohri
authors: Hiroshi
authors: H
authors: Arai
authors: Masako
authors: M
authors: Taniike
authors: Keiichi
authors: K
authors: Ozono
mesh_terms: D002648:Child; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D027501:Monocarboxylic Acid Transporters / Q000235:genetics*; D015997:Neonatal Screening; D010641:Phenotype; D027981:Symporters; D013959:Thyroid Diseases / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology; D013974:Thyroxine / Q000627:therapeutic use*
chemical_list: D027501:Monocarboxylic Acid Transporters; C090735:SLC16A2 protein, human; D027981:Symporters; D013974:Thyroxine