title: Activation of brown adipose tissue in hypothyroidism.
abstract: BACKGROUND
  Brown adipose tissue (BAT) attracts growing interest as a potential therapeutic target for obesity and diabetes. Hyperthyroidism is well-known to increase BAT activity, but the role of hypothyroidism is controversial. We aimed to investigate the association between different thyroid hormone (TH) states and BAT activity.
  
  
  METHODS
  FDG-PET studies were retrospectively evaluated in thyroid cancer patients after total thyroidectomy both at euthyroidism during TH replacement or at hypothyroidism after TH cessation. Serum TH levels were compared between patients with active BAT and control patients with non-active BAT matched for age, gender, and body mass index. Additionally, animal experiments with controls (n = 5) and hypothyroid rats (n = 5) were performed.
  
  
  RESULTS
  Out of 124 patients, 6 patients with active BAT were identified. These patients showed significantly higher thyroid-stimulating hormone (TSH) levels than matched controls (P < 0.05). In animal experiments, all hypothyroid animals showed BAT activation at room temperature (24 °C), whereas controls did not (P < 0.001). Increased BAT activity was also confirmed by increased expression of UCP-1 and D2.
  
  
  CONCLUSIONS
  Increased BAT metabolism appears to be related with hypothyroidism, which might be the result of a feedback mechanism to maintain body temperature in a state of reduced basal thermogenesis. Future research needs to explore the underlying mechanistic and biological implications.
authors.affiliation: a Department of Nuclear Medicine , University Hospital Würzburg , Würzburg , Germany.
authors.forename: Constantin
authors.initials: C
authors.lastname: Lapa
authors.affiliation: a Department of Nuclear Medicine , University Hospital Würzburg , Würzburg , Germany.|b Research Centre , Nihon Medi-Physics Co Ltd , Chiba , Japan.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Maya
authors.affiliation: c Institute of Clinical Epidemiology and Biometry, University of Würzburg , Würzburg , Germany.|d Comprehensive Heart Failure Center , University Hospital Würzburg , Würzburg , Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Wagner
authors.affiliation: e Department of Internal Medicine I, Division of Cardiology , University Hospital Würzburg , Würzburg , Germany.
authors.forename: Paula
authors.initials: P
authors.lastname: Arias-Loza
authors.affiliation: a Department of Nuclear Medicine , University Hospital Würzburg , Würzburg , Germany.
authors.forename: Rudolf A
authors.initials: RA
authors.lastname: Werner
authors.affiliation: a Department of Nuclear Medicine , University Hospital Würzburg , Würzburg , Germany.|f Ahmanson Translational Imaging Division, Department of Molecular and Medical Pharmacology , David Geffen School of Medicine at UCLA , USA.
authors.forename: Ken
authors.initials: K
authors.lastname: Herrmann
authors.affiliation: a Department of Nuclear Medicine , University Hospital Würzburg , Würzburg , Germany.|d Comprehensive Heart Failure Center , University Hospital Würzburg , Würzburg , Germany.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Higuchi
mesh_terms: D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001831:Body Temperature / Q000502:physiology; D016022:Case-Control Studies; D002648:Child; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007037:Hypothyroidism / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D012189:Retrospective Studies; D013696:Temperature; D013963:Thyroid Hormones / Q000097:blood*; D013964:Thyroid Neoplasms / Q000601:surgery; D013965:Thyroidectomy / Q000379:methods; D013972:Thyrotropin / Q000097:blood*; D055815:Young Adult
chemical_list: D013963:Thyroid Hormones; D019788:Fluorodeoxyglucose F18; D013972:Thyrotropin
keywords: Brown adipose tissue; PET/CT; TSH; hypothyroidism; thyroid hormone