title: Variable Cold-Induced Brown Adipose Tissue Response to Thyroid Hormone Status.
abstract: In addition to its role in adaptive thermogenesis, brown adipose tissue (BAT) may protect from weight gain, insulin resistance/diabetes, and metabolic syndrome. Prior studies have shown contradictory results regarding the influence of thyroid hormone (TH) levels on BAT volume and activity. The aim of this pilot study was to gain further insights regarding the effect of TH treatment on BAT function in adult humans by evaluating the BAT mass and activity prospectively in six patients, first in the hypothyroid and then in the thyrotoxic phase.
  
  
  
  The study subjects underwent 18F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) scanning after cold exposure to measure BAT mass and activity while undergoing treatment for differentiated thyroid cancer, first while hypothyroid following TH withdrawal at the time of the radioactive iodine treatment and then three to six months after starting TH suppressive treatment when they were iatrogenically thyrotoxic. Thermogenic and metabolic parameters were measured in both phases.
  
  
  
  All study subjects had detectable BAT under cold stimulation in both the hypothyroid and thyrotoxic state. The majority but not all (4/6) subjects showed an increase in detectable BAT volume and activity under cold stimulation between the hypothyroid and thyrotoxic phase (total BAT volume: 72.0 ± 21.0 vs. 87.7 ± 16.5 mL, p = 0.25; total BAT activity 158.1 ± 72.8 vs. 189.0 ± 55.5 SUV*g/mL, p = 0.34). Importantly, circulating triiodothyronine was a stronger predictor of energy expenditure changes compared with cold-induced BAT activity.
  
  
  
  Iatrogenic hypothyroidism lasting two to four weeks does not prevent cold-induced BAT activation, while the use of TH to induce thyrotoxicosis does not consistently increase cold-induced BAT activity. It remains to be determined which physiological factors besides TH play a role in regulating BAT function.
authors.affiliation: 1 Department of Medicine, Beth Israel Deaconess Medical Center , Boston, Massachusetts.
authors.forename: Alina
authors.initials: A
authors.lastname: Gavrila
authors.affiliation: 2 Department of Surgery, Beth Israel Deaconess Medical Center , Boston, Massachusetts.
authors.forename: Per-Olof
authors.initials: PO
authors.lastname: Hasselgren
authors.affiliation: 3 Harvard Catalyst Clinical Research Center, Beth Israel Deaconess Medical Center , Boston, Massachusetts.
authors.forename: Allison
authors.initials: A
authors.lastname: Glasgow
authors.affiliation: 3 Harvard Catalyst Clinical Research Center, Beth Israel Deaconess Medical Center , Boston, Massachusetts.
authors.forename: Ashley N
authors.initials: AN
authors.lastname: Doyle
authors.affiliation: 3 Harvard Catalyst Clinical Research Center, Beth Israel Deaconess Medical Center , Boston, Massachusetts.
authors.forename: Alice J
authors.initials: AJ
authors.lastname: Lee
authors.affiliation: 4 Section of Integrative Physiology and Metabolism, Research Division, Joslin Diabetes Center , Harvard Medical School, Boston, Massachusetts.
authors.forename: Peter
authors.initials: P
authors.lastname: Fox
authors.affiliation: 1 Department of Medicine, Beth Israel Deaconess Medical Center , Boston, Massachusetts.
authors.forename: Shiva
authors.initials: S
authors.lastname: Gautam
authors.affiliation: 1 Department of Medicine, Beth Israel Deaconess Medical Center , Boston, Massachusetts.
authors.forename: James V
authors.initials: JV
authors.lastname: Hennessey
authors.affiliation: 5 Department of Radiology, Beth Israel Deaconess Medical Center , Boston, Massachusetts.
authors.forename: Gerald M
authors.initials: GM
authors.lastname: Kolodny
authors.affiliation: 1 Department of Medicine, Beth Israel Deaconess Medical Center , Boston, Massachusetts.|4 Section of Integrative Physiology and Metabolism, Research Division, Joslin Diabetes Center , Harvard Medical School, Boston, Massachusetts.|6 Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland.
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Cypess
mesh_terms: D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging / Q000378:metabolism*; D000328:Adult; D002291:Carcinoma, Papillary / Q000601:surgery; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007037:Hypothyroidism / Q000000981:diagnostic imaging / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D000072078:Positron Emission Tomography Computed Tomography; D022722:Thermogenesis / Q000502:physiology*; D013963:Thyroid Hormones / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000601:surgery; D013965:Thyroidectomy; D013971:Thyrotoxicosis / Q000000981:diagnostic imaging / Q000378:metabolism*; D055815:Young Adult
chemical_list: D013963:Thyroid Hormones; D019788:Fluorodeoxyglucose F18
keywords: brown adipose tissue; hypothyroidism; thermogenesis; thyroid hormone; thyrotoxicosis