title: Suppression of hypothalamic deiodinase type II activity blunts TRH mRNA decline during fasting.
abstract: Fasting is characterized by disrupted thyroid feedback, with suppressed levels of thyroid hormones and paraventricular thyrotropin releasing hormone (TRH). We found that third ventricle administration of the deiodinase inhibitor, iopanoic acid, dose-dependently reduced deiodinase type II (DII) activity selectively in the hypothalamus. This suppression of DII by iopanoic acid during fasting prevented elevated DII activity and blunted the decline in hypothalamic TRH mRNA levels. Because fasting-induced elevation in hypothalamic DII activity is paralleled by increased hypothalamic T3 concentration, our study suggests that T3 formation by DII in the hypothalamus is the cause of disrupted thyroid feedback during fasting.
authors.affiliation: Department of Obstetrics, Gynecology and Reproductive Sciences, Yale University School of Medicine, 333 Cedar St. FMB 339, New Haven, CT 06520, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Coppola
authors.forename: Jeniter
authors.initials: J
authors.lastname: Hughes
authors.forename: Emanuela
authors.initials: E
authors.lastname: Esposito
authors.forename: Luigi
authors.initials: L
authors.lastname: Schiavo
authors.forename: Rosaria
authors.initials: R
authors.lastname: Meli
authors.forename: Sabrina
authors.initials: S
authors.lastname: Diano
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D005215:Fasting; D025461:Feedback, Physiological; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D017403:In Situ Hybridization; D007453:Iodide Peroxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007480:Iopanoic Acid / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013973:Thyrotropin-Releasing Hormone / Q000235:genetics / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D007453:Iodide Peroxidase; D007480:Iopanoic Acid