Constantin Lapa1, Yoshifumi Maya1,2, Martin Wagner3,4, Paula Arias-Loza5, Rudolf A Werner1, Ken Herrmann1,6, Takahiro Higuchi1,4. 1. a Department of Nuclear Medicine , University Hospital Würzburg , Würzburg , Germany. 2. b Research Centre , Nihon Medi-Physics Co Ltd , Chiba , Japan. 3. c Institute of Clinical Epidemiology and Biometry, University of Würzburg , Würzburg , Germany. 4. d Comprehensive Heart Failure Center , University Hospital Würzburg , Würzburg , Germany. 5. e Department of Internal Medicine I, Division of Cardiology , University Hospital Würzburg , Würzburg , Germany. 6. f Ahmanson Translational Imaging Division, Department of Molecular and Medical Pharmacology , David Geffen School of Medicine at UCLA , USA.
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.
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 cancerpatients 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 hypothyroidrats (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.
Entities:
Keywords:
Brown adipose tissue; PET/CT; TSH; hypothyroidism; thyroid hormone
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