Department of Nuclear Medicine; Leipzig, Germany.
Medical Department III-Endocrinology, Nephrology, Rheumatology; Leipzig, Germany.
Thyroid. 2021 Mar;31(3):519-527. doi: 10.1089/thy.2019.0806. Epub 2020 Nov 18.
Positron emission tomography (PET) has provided evidence that adult humans retain metabolically active brown adipose tissue (BAT) depots. Thyroid hormones (TH) stimulate BAT thermogenesis by central and peripheral mechanisms. However, the effect of hyperthyroidism on BAT activity and BAT volume in humans is yet not fully understood. The aim of this study was to investigate the effect of TH on (i) the metabolic activity of brown and white adipose tissue (WAT) depots, (ii) on abdominal visceral and subcutaneous adipose tissue area, and (iii) on serum levels of metabolically active cytokines. Nineteen patients with overt hyperthyroidism were investigated through repeated 2-[F]fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography (2-[F]FDG PET/CT) in the hyperthyroid and in the euthyroid state. The 2-[F]FDG uptake was calculated as standard uptake ratio with blood pool as reference. Fat areas were quantified by means of CT segmentation. Serum levels of fetuin A and B, fibroblast growth factor 21, adipocyte fatty acid-binding protein (AFABP), retinol-binding protein 4, pro-enkephalin, pro-neurotensin, and neuregulin 4 were determined in the hyperthyroid and in the euthyroid state for each subject. 2-[F]FDG uptake was increased in the hyperthyroid state in BAT in comparison with the euthyroid phase ( = 0.001). There was no correlation between serum free triiodothyronine (fT3) and free thyroxine (fT4) levels and 2-[F]FDG uptake in BAT or WAT. In the hyperthyroid state, fT3 levels were positively associated with skeletal muscle standardized uptake value ratios. Areas of visceral adipose tissue and skeletal muscle were significantly decreased in hyperthyroidism. AFABP levels correlated positively with fT3 ( = 0.031, β = 0.28) and fT4 ( = 0.037, β = 0.27) in the hyperthyroid state. Our results suggest that the contribution of increased TH levels to the glucose uptake of BAT and WAT is low compared with that of the skeletal muscle. Hyperthyroid subjects have reduced areas of visceral adipose tissue and increased AFABP levels.
正电子发射断层扫描（PET）已经提供了证据，证明成年人保留了代谢活跃的棕色脂肪组织（BAT）。甲状腺激素（TH）通过中枢和外周机制刺激 BAT 产热。然而，甲状腺功能亢进症对人类 BAT 活性和 BAT 体积的影响尚未完全了解。本研究的目的是研究 TH 对（i）棕色和白色脂肪组织（WAT）沉积的代谢活性、（ii）腹部内脏和皮下脂肪组织面积、以及（iii）代谢活跃细胞因子的血清水平的影响。19 例显性甲状腺功能亢进症患者通过重复 2-[F]氟-2-脱氧-d-葡萄糖正电子发射断层扫描/计算机断层扫描（2-[F]FDG PET/CT）在甲状腺功能亢进症和甲状腺功能正常状态下进行了研究。2-[F]FDG 摄取作为标准摄取比，以血池为参考。通过 CT 分割定量脂肪面积。在甲状腺功能亢进症和甲状腺功能正常状态下，为每位受试者测定了胎球蛋白 A 和 B、成纤维细胞生长因子 21、脂肪细胞脂肪酸结合蛋白（AFABP）、视黄醇结合蛋白 4、前啡肽、前神经降压素和神经调节蛋白 4 的血清水平。与甲状腺功能正常阶段相比，甲状腺功能亢进症患者的 BAT 中 2-[F]FDG 摄取增加（=0.001）。血清游离三碘甲状腺原氨酸（fT3）和游离甲状腺素（fT4）水平与 BAT 或 WAT 中 2-[F]FDG 摄取之间无相关性。在甲状腺功能亢进症状态下，fT3 水平与骨骼肌标准化摄取值呈正相关。甲状腺功能亢进症时内脏脂肪组织和骨骼肌面积明显减少。AFABP 水平与 fT3（=0.031，β=0.28）和 fT4（=0.037，β=0.27）在甲状腺功能亢进症状态下呈正相关。我们的结果表明，与骨骼肌相比，TH 水平升高对 BAT 和 WAT 葡萄糖摄取的贡献较低。甲状腺功能亢进症患者的内脏脂肪组织面积减少，AFABP 水平升高。
