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词汇介绍
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解析
triiodothyronine 英 /traɪ,aɪədə(ʊ)'θaɪrəniːn/ 美 /aɪədo'θaɪrənin/
释 义 n. 三碘甲状腺氨酸
例 句 Triiodothyronine (T3) and insulin can promote the cell's metabolism of sugar, fat and protein, and accelerate the cell's growth. 三碘甲状腺原氨酸（T3）和胰岛素能促进糖、脂肪和蛋白质三大物质的代谢，加速细胞的氧化过程。
概述
概述
三碘甲腺原氨酸，也称为T3，是一种甲状腺激素。它几乎影响身体的每一个生理过程，包括生长发育，新陈代谢，体温和心率。
机制
T3和T4与核受体（甲状腺激素受体）结合。T3和T4虽然是亲脂性的，但不能被动地扩散通过靶细胞的磷脂双层，而是依赖于跨膜碘甲状腺原氨酸转运蛋白。T3和T4的亲脂性需要它们与蛋白质载体甲状腺结合蛋白（TBG）结合（甲状腺素结合球蛋白，甲状腺素结合前白蛋白和白蛋白）用于血液中的运输。甲状腺受体与基因启动子中的反应元件结合，从而使它们能够激活或抑制转录。通过甲状腺受体调节组织对T 3的敏感性。
转运
T3和T4在血液中携带，与血浆蛋白结合。这具有增加激素的半衰期和降低外周组织吸收的速率的作用。这两种激素有三种主要蛋白质结合在一起。甲状腺素结合球蛋白（TBG）是一种糖蛋白，其对T4的亲和力高于对T3的亲和力。运甲状腺素蛋白也是一种糖蛋白，但仅携带T4，对T3几乎没有任何亲和力。两种激素以低亲和力结合血清白蛋白，但由于白蛋白的大量可用性，它具有高容量。
生长需要
T3对发育中的胚胎和婴儿有深远的影响。它会影响肺部并影响中枢神经系统的出生后生长。它刺激髓鞘的产生，神经递质的产生和轴突的生长。它对骨骼的线性生长也很重要。
生理功能
甲状腺激素的作用是增加蛋白质周转率。这可能在长期热量限制和适当蛋白质方面起到适应性作用。当卡路里短缺时，蛋白质周转的减少可能会改善短缺的影响。
复制标题低血清三碘甲状腺原氨酸水平的类风湿关节炎患者的持续性贫血和低白蛋白血症
发表时间：2019-08-08
影响指数：2.0
作者： Hideaki Tsuji
期刊：MOD RHEUMATOL
Serum triiodothyronine (T3) levels can be decreased in patients with chronic inflammatory conditions, and this finding is called ‘low-T3 syndrome’ or ‘euthyroid sick syndrome’. Generally, T3 is produced by transformation from thyroxine (T4) under normal homeostatic conditions. In low-T3 syndrome, the thyroid gland is normal, but T3 production by conversion from T4 is decreased secondary to suppression of thyrotropin-releasing hormone (TRH) and thyroid-stimulating hormone (TSH) in the presence of inflammation. Rheumatoid arthritis (RA) is an inflammatory disease characterized by joint destruction and physical dysfunction. Serum free T3 (fT3) levels can be decreased in patients with RA, and inflammatory cytokines such as tumor necrosis factor (TNF) or interleukin (IL)-6, key molecules in the pathogenesis of RA, also play important roles in low T3 syndrome. For example, TNF and IL-6 inhibit the conversion of T4 to T3 and inactivate T3. These findings suggest that RA disease activity and serum fT3 levels are closely linked via inflammatory cytokines such as TNF and IL-6. Low serum T3 levels are reported in 7%–52% of RA patients. One of the reasons for the wide-range of frequencies in low-T3 RA patients may be an incomplete definition of ‘low-T3 patients.’ For example, patients with low-T3 caused by autoimmune thyroid diseases (ATD) or those who are taking anti-thyroid medications were included in previous analyses. Furthermore, because of advances in RA treatment, the clinical characteristics of RA patients may have changed. Therefore, the prevalence and characteristics of RA patients with low-T3 levels have not been fully addressed. In this study, we examined fT3, free T4 (fT4), and TSH levels in RA patients. After excluding patients with ATD or those taking anti-thyroid medications, we analyzed the clinical characteristics of RA patients with low-fT3 levels. We also followed patients with low-fT3 levels and compared the clinical characteristics of patients whose fT3 levels normalized with those who showed persistently low-fT3 levels.
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