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首页> 外文期刊>American Journal of Physiology >Serum thyroid hormone levels may not accurately reflect thyroid tissue levels and cardiac function in mild hypothyroidism
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Serum thyroid hormone levels may not accurately reflect thyroid tissue levels and cardiac function in mild hypothyroidism

机译：在轻度甲状腺功能减退症中，血清甲状腺激素水平可能无法准确反映甲状腺组织水平和心脏功能

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The link between thyroid dysfunction and cardiovascular diseases has been recognized for more than 100 years. Although overt hypothyroidism leads to impaired cardiac function and possibly heart failure, the cardiovascular consequences of borderline low thyroid function are not clear. Establishment of a suitable animal model would be helpful. In this study, we characterized a rat model to study the relationship between cardiovascular function and graded levels of thyroid activity. We used rats with surgical thyroidectomy and subcutaneous implantation of slow release pellets with three different T_4 doses for 3 wk. In terminal experiments, cardiac function was evaluated by echocardiograms and hemodynamics. Myocardial arteriolar density was also quantified morphometrically. Thyroid hormone levels in serum and heart tissue were determined by RIA assays. Thyroidectomy alone led to cardiac atrophy, severe cardiac dysfunction, and a dramatic loss of arterioles. The low T_4 dose normalized serum T_3 and T_4 levels, but cardiac tissue T_3 and T_4 remained below normal. Low-dose T_4 failed to prevent cardiac atrophy or restore cardiac function and arteriolar density to normal values. All cardiac function parameters and myocardial arteriolar density were normalized with the middle dose of T_4, whereas the high dose produced hyperthyroidism. Our results show that thyroid hormones are important regulators of cardiac function and myocardial arteriolar density. This animal model will be useful in studying the pathophysiological consequences of mild thyroid dysfunction. Results also suggest that cardiac function may provide valuable supplemental information in proper diagnosis of mild thyroid conditions.
机译：甲状腺功能障碍与心血管疾病之间的联系已被公认超过100年。尽管明显的甲状腺功能减退症会导致心脏功能受损，甚至可能导致心力衰竭，但尚不清楚临界甲状腺功能低下的心血管后果。建立合适的动物模型将有所帮助。在这项研究中，我们表征了一个大鼠模型，以研究心血管功能与甲状腺活动分级水平之间的关系。我们用外科甲状腺切除术和皮下植入三种不同T_4剂量的缓释微丸植入大鼠3周。在终末实验中，通过超声心动图和血液动力学评估心脏功能。心肌小动脉密度也通过形态计量学定量。通过RIA测定法测定血清和心脏组织中的甲状腺激素水平。单独进行甲状腺切除术会导致心脏萎缩，严重的心脏功能障碍和小动脉的大量丢失。低T_4剂量可使血清T_3和T_4正常化，但心脏组织T_3和T_4仍低于正常水平。小剂量T_4无法预防心脏萎缩或无法将心脏功能和小动脉密度恢复至正常值。所有的心功能参数和心肌小动脉密度均以中剂量T_4标准化，而高剂量则产生甲亢。我们的结果表明，甲状腺激素是心脏功能和心肌小动脉密度的重要调节剂。这种动物模型将有助于研究轻度甲状腺功能不全的病理生理后果。结果还表明，心脏功能可能为轻度甲状腺疾病的正确诊断提供有价值的补充信息。

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