1 Department of Endocrinology, Ghent University Hospital , Ghent, Belgium .
Thyroid. 2014 Feb;24(2):223-31. doi: 10.1089/thy.2013.0314. Epub 2013 Nov 14.
We have previously shown that in healthy young men, a less favorable body composition is associated with higher free triiodothyronine (fT3) levels within the euthyroid range. Besides, a higher free-triiodothyronine-to-free-thyroxin (fT3-to-fT4) ratio has been related to a less favorable metabolic phenotype and more placental growth in pregnant women. In the present study, we therefore investigated whether serum thyrotropin (TSH), thyroid hormone levels, and the fT3-to-fT4 ratio are associated with metabolic and adiposity-related cardiovascular risk markers in a healthy population of middle-aged euthyroid men and women.
Thyroid parameters were measured in 2524 generally healthy subjects from the Asklepios Study (35-55 years, mean age 46 years). Analyses were restricted to 2315 subjects (1138 women and 1177 men), not using thyroid medication, not having anti-TPO levels above clinical cutoff values or TSH levels outside the reference range (0.27-4.2 mU/L). Twenty-seven percent of the women and 47.5% of the men were overweight, while 13% of women and 17% of men were obese. Twenty percent of the subjects were active smokers. Serum thyroid function parameters were determined by electrochemiluminescence.
fT3 and the fT3-to-fT4 ratio were positively related to body mass index (BMI), waist circumference, and components of metabolic syndrome, that is, triglycerides, systolic and diastolic blood pressure, and fasting plasma glucose, and negatively with HDL-cholesterol levels, whereas fT4 was negatively associated with BMI, waist circumference, and triglycerides (p<0.001). TSH related positively with total cholesterol levels (p<0.01), triglycerides, and systolic and diastolic blood pressure (p<0.001). The fT3-to-fT4 ratio was further positively associated with the adiposity-related inflammation markers interleukin-6 and high-sensitivity C-reactive protein and to pulse wave velocity. All associations were adjusted for sex, age, height, and smoking, and most associations persisted after additional adjustment for weight or waist circumference.
In healthy euthyroid middle-aged men and women, higher fT3 levels, lower fT4 levels, and thus a higher fT3-to-fT4 ratio are consistently associated with various markers of unfavorable metabolic profile and cardiovascular risk.
我们之前的研究表明，在健康的年轻男性中，甲状腺功能正常范围内游离三碘甲状腺原氨酸（fT3）水平较高与体脂组成较差相关。此外，游离三碘甲状腺原氨酸与游离甲状腺素（fT3 与 fT4）比值较高与代谢表型较差和孕妇胎盘生长较多相关。在本研究中，我们因此研究了甲状腺刺激素（TSH）、甲状腺激素水平和 fT3 与 fT4 比值是否与健康中年甲状腺功能正常的男性和女性的代谢和肥胖相关的心血管风险标志物相关。
在 Asklepios 研究中（35-55 岁，平均年龄 46 岁），我们测量了 2524 名一般健康受试者的甲状腺参数。分析仅限于 2315 名受试者（1138 名女性和 1177 名男性），他们未服用甲状腺药物，抗甲状腺过氧化物酶水平未超过临床临界值或 TSH 水平不在参考范围（0.27-4.2 mU/L）内。27%的女性和 47.5%的男性超重，而 13%的女性和 17%的男性肥胖。20%的受试者为主动吸烟者。血清甲状腺功能参数通过电化学发光法测定。
fT3 和 fT3 与 fT4 的比值与体重指数（BMI）、腰围和代谢综合征的成分（即甘油三酯、收缩压和舒张压以及空腹血糖）呈正相关，与高密度脂蛋白胆固醇水平呈负相关，而 fT4 与 BMI、腰围和甘油三酯呈负相关（p<0.001）。TSH 与总胆固醇水平（p<0.01）、甘油三酯以及收缩压和舒张压呈正相关（p<0.001）。fT3 与 fT4 的比值与肥胖相关的炎症标志物白细胞介素-6 和高敏 C 反应蛋白以及脉搏波速度进一步呈正相关。所有关联均在调整性别、年龄、身高和吸烟的情况下进行，并且大多数关联在进一步调整体重或腰围后仍然存在。
在健康的甲状腺功能正常的中年男性和女性中，较高的 fT3 水平、较低的 fT4 水平以及较高的 fT3 与 fT4 比值与各种不利代谢特征和心血管风险标志物持续相关。
