In aged population, the association of thyroid hormones on physical performance, especially within their normal range, has yet to be elucidated. In this study, individuals with low serum free T3/free T4 were likely to have low muscle mass and impaired physical performance. PURPOSE We aimed to evaluate the associations of muscle mass, strength, and physical performance with thyroid hormone in an aged euthyroid population from a community-based cohort. METHODS We examined 918 men aged over 60 years and 1215 postmenopausal women from the Ansung cohort study. Appendicular skeletal muscle mass divided by square of height (ASM/ht2) was used as the muscle mass index. Hand grip strength was measured using a hydraulic dynamometer. Physical performance was assessed using the short physical performance battery (SPPB). RESULTS Participants with higher tertiles of free T3 and free T3/free T4 were younger and had higher ASM/ht2, stronger hand grip strength, and higher SPPB scores than those in the lower tertiles. In adjusted models, men within higher tertiles of free T3 had higher ASM/ht2 compared with those within lower tertiles (p = 0.033), whereas subjects with higher tertiles of free T4 had lower ASM/ht2 compared with those within lower tertiles (p = 0.043). Subjects within higher tertiles of free T3/free T4 had higher ASM/ht2 (p < 0.001) and better physical performance (p = 0.048) than those within lower tertiles after adjustments. However, free T3, free T4, or free T3/free T4 was not related to hand grip strength after adjustment for covariates. CONCLUSION Our results thus indicate that in an aged euthyroid population, low serum free T3/free T4 was a better index for low muscle mass and impaired physical performance than serum free T3 or free T4 alone.

中文翻译：

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游离T3与游离T4的比率低与社区居住的老年人口的肌肉质量低和身体机能受损有关。

在老年人群中，甲状腺激素与身体机能的关系，特别是在正常范围内，尚待阐明。在这项研究中，血清游离T3 /游离T4低的个体可能具有低肌肉质量和受损的身体机能。目的我们的目的是评估来自社区队列的老年正常甲状腺人群的肌肉质量，力量和身体机能与甲状腺激素的相关性。方法我们从Ansung队列研究中检查了918名60岁以上的男性和1215名绝经后的女性。附肢骨骼肌质量除以身高平方（ASM / ht2）作为肌肉质量指数。使用液压测功机测量手握强度。使用短物理性能电池（SPPB）评估了物理性能。结果游离T3和游离T3 /游离T4的三分位数较高的参与者比低三分位数的参与者更年轻，并且具有更高的ASM / ht2，更强的手握强度和更高的SPPB评分。在调整后的模型中，游离T3较高三分位数的男性与较低三分位数中的男性相比具有较高的ASM / ht2（p = 0.033），而游离T4较高三分位数的受试者相比较低三分位数中的男性具有较低的ASM / ht2（p = 0.043）。调整后，游离T3 /游离T4较高三分位数内的受试者比较低三分位数内的受试者具有更高的ASM / ht2（p <0.001）和更好的身体表现（p = 0.048）。但是，调整协变量后，游离T3，游离T4或游离T3 /游离T4与握力无关。结论因此，我们的结果表明，在正常年龄的甲状腺人群中，