High free triiodothyronine, and free-triiodothyronine-to-free-thyroxine ratio are associated with metabolic syndrome in a euthyroid employee population: the Zhejiang Zhenhai study

Abstract

Objective: To elaborate the link of thyroid hormones and metabolic syndrome in a Chinese euthyroid employee population with metabolic syndrome component(s). Methods: An annual health check-up was performed on employees in 2019. Anthropometric parameters, metabolic parameters and thyroid function were measured. A questionnaire was used in conjunction with Zhenhai Lianhua Hospital database to receive employees' medication records and thyroid surgical history records. Results: A total of 5486 eligible employees were included, the prevalence of metabolic syndrome was generally higher in males than in females (38.9% vs. 30.4%, P < 0.001). Among employees with central obesity, hypertriglyceridemia, hyperglycemia, hypertension, and low high density lipoprotein cholesterol, the prevalence of metabolic syndrome was 68.8%, 63.6%, 68.2%, 48.8% and 60.0% in males and 72.6%, 63.3%, 61.3%, 42.3% and 42.3% in females, respectively. Logistic regression analysis showed that thyroid stimulating hormone (TSH) and Free thyroxine (FT4) quartiles had no significant impact on metabolic syndrome; Free Triiodothyronine / Free thyroxine (FT3/FT4), and Free Triiodothyronine (FT3) quartiles were positively associated with the increased odds ratio for metabolic syndrome and dyslipidemia (hypertriglyceridemia, low HDL-C), regardless of gender. In males, FT3, FT3/FT4 quartiles were positively associated with the odds ratio for central obesity, whereas FT4 quartiles were negatively associated; both FT3 and FT4 quartiles were positively associated with increased odds ratio of hyperglycemia, while similar results were not observed in females. Interaction analysis indicated no significant effect of gender and thyroid hormone interactions on risk of metabolic syndrome. Conclusion: High FT3, FT3/FT4 were strongly linked with metabolic syndrome and dyslipidemia in our study, even in the euthyroid individuals. Tighter control of thyroid function was necessary for those with pre-existing metabolic syndrome component(s).

Association between metabolic score of visceral fat and carotid atherosclerosis in Chinese health screening population: a cross-sectional study

“…Baseline clinical data collection and evaluation were performed using established protocols from previous studies [ 23 ]. Baseline clinical data for this study were determined based on previous research [ 24 ].…”