title: Lower serum free thyroxine levels are associated with metabolic syndrome in a Chinese population.
abstract: Thyroid hormones play an important role in regulating energy homeostasis and lipid and glucose metabolism. This study assessed the relationship between free thyroxine and clinical features of metabolic syndrome (MS). A total of 4,938 Taiwanese subjects (2,891 men and 2,047 women with a mean age of 50.1+/-12.6 years) with normal serum free thyroxine levels were enrolled. A modified National Cholesterol Education Program definition of MS was adopted substituting body mass index (BMI) for waist circumference. Serum free thyroxine concentrations were determined by immunoassay. Overall, 14% of subjects had a high fasting glucose, 27% had high blood pressure, 14% had high serum total triglyceride, 8% had low high-density lipoprotein cholesterol, and 18% were obese. The serum free thyroxine concentrations showed a statistically significant correlation with triglyceride and body mass index, respectively (P<.01), but not with blood pressure, glucose level, or high-density lipoprotein cholesterol level. According to the presence of 0, 1, 2, and 3 or more features of MS, age and sex-adjusted means of serum free thyroxine were 17.8+/-3.7, 17.6+/-3.7, 17.5+/-3.7, and 17.1+/-3.3 pmol/L, respectively, with a modest, but statistically significant, decreasing trend (P<.05). When comparing subjects in the highest and lowest quartile of free thyroxine, the former group demonstrated a 2-fold decrease in the odds ratio for MS with 3 or more metabolic features. Low circulating free thyroxine levels, albeit normal, were associated with MS in a Chinese population. Further study is necessary to document the role of thyroid hormones in metabolic abnormalities of MS.
authors.affiliation: Division of Endocrinology and Metabolism, Department of Medicine, Taichung Veterans General Hospital, Taichung 407, Taiwan. sylin@vghtc.gov.tw
authors.forename: Shih-Yi
authors.initials: SY
authors.lastname: Lin
authors.forename: Ya-Yu
authors.initials: YY
authors.lastname: Wang
authors.forename: Pi-Haw
authors.initials: PH
authors.lastname: Liu
authors.forename: Wen-An
authors.initials: WA
authors.lastname: Lai
authors.forename: Wayne Huey-Herng
authors.initials: WH
authors.lastname: Sheu
mesh_terms: D000328:Adult; D017677:Age Distribution; D044466:Asian People / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D015228:Hypertriglyceridemia / Q000208:ethnology / Q000378:metabolism; D008297:Male; D024821:Metabolic Syndrome / Q000208:ethnology* / Q000378:metabolism*; D008875:Middle Aged; D009765:Obesity / Q000208:ethnology / Q000378:metabolism; D015995:Prevalence; D017678:Sex Distribution; D013624:Taiwan / Q000453:epidemiology; D013974:Thyroxine / Q000097:blood*
chemical_list: D013974:Thyroxine