Metabolic syndrome (MetS) and thyroid dysfunction are common in clinical practice. The objectives of this review are to discuss some proposed mechanisms by which thyroid dysfunctions may lead to MetS, to describe the bidirectional relationship between thyroid hormones (THs) and adiposity and finally, to resume a list of recent studies in humans that evaluated possible associations between thyroid hormone status and MetS or its clinical components. Not solely THs, but also its metabolites regulate metabolic rate, influencing adiposity. The mechanisms enrolled are related to its direct effect on adenosine triphosphate (ATP) utilization, uncoupling synthesis of ATP, mitochondrial biogenesis, and its inotropic and chronotropic effects. THs also act controlling core body temperature, appetite, and sympathetic activity. In a bidirectional way, thyroid function is affected by adiposity. Leptin is one of the hallmarks, but the pro-inflammatory cytokines and also insulin resistance impact thyroid function and perhaps its structure. MetS development and weight gain have been positively associated with thyroid-stimulating hormone (TSH) in several studies. Adverse glucose metabolism may be related to hyperthyroidism, but also to reduction of thyroid function or higher serum TSH, as do abnormal serum triglyceride levels. Hypo- and hyperthyroidism have been related to higher blood pressure (BP), that may be consequence of genomic or nongenomic action of THs on the vasculature and in the heart. In summary, the interaction between THs and components of MetS is complex and not fully understood. More longitudinal studies controlling each of all confounding variables that interact with endpoints or exposure factors are still necessary.

代谢综合征（MetS）和甲状腺功能障碍在临床实践中很常见。本综述的目的是讨论甲状腺功能障碍可能导致 MetS 的一些拟议机制，描述甲状腺激素 (THs) 和肥胖之间的双向关系，最后恢复一系列最近的人类研究，这些研究评估了甲状腺激素和肥胖之间可能存在的关联。甲状腺激素状态和 MetS 或其临床成分。不仅仅是 TH，它的代谢物也调节代谢率，影响肥胖。纳入的机制与其对三磷酸腺苷 (ATP) 利用、ATP 解偶联合成、线粒体生物发生及其正性肌力和变时性作用的直接影响有关。TH 还可以控制核心体温、食欲和交感神经活动。甲状腺功能以双向方式受到肥胖的影响。瘦素是标志之一，但促炎细胞因子和胰岛素抵抗会影响甲状腺功能及其结构。多项研究表明，代谢综合征的发展和体重增加与促甲状腺激素 (TSH) 呈正相关。葡萄糖代谢不良可能与甲状腺功能亢进有关，但也与甲状腺功能降低或血清 TSH 升高以及血清甘油三酯水平异常有关。甲状腺功能减退症和甲状腺功能亢进症与血压升高有关，这可能是 TH 对脉管系统和心脏的基因组或非基因组作用的结果。总之，TH 和 MetS 成分之间的相互作用是复杂的且尚未完全了解。仍然需要进行更多的纵向研究来控制与终点或暴露因素相互作用的所有混杂变量。