title: Lower-normal TSH is associated with better metabolic risk factors: A cross-sectional study on Spanish men.
abstract: OBJECTIVE
  Subclinical thyroid conditions, defined by normal thyroxin (T4) but abnormal thyroid-stimulating hormone (TSH) levels, may be associated with cardiovascular and metabolic risk. More recently, TSH levels within the normal range have been suggested to be associated with metabolic syndrome and cardiovascular risk. This work studies the linearity of the relationship between metabolic syndrome and TSH across the euthyroid range.
  
  
  RESULTS
  We studied 3533 male participants of the Aragon Workers' Health Study (AWHS) with normal TSH and free T4 levels, across quintiles of these variables, after adjusting for age, alcohol intake, and smoking. Compared with the lowest TSH quintile, the odds ratios for metabolic syndrome at the higher quintiles, which indicate lower thyroid function, were 1.34 (1.04, 1.73), 1.56 (1.21, 2.01), 1.57 (1.22, 2.03), and 1.71 (1.32, 2.21). The lowest free T4 quintile also showed an odds ratio of 1.49 (1.16, 1.90) with respect to the highest quintile. In addition, spline models showed departures from linearity: the risk of metabolic syndrome mostly increases at TSH values below the median (sample half-closest to subclinical hyperthyroidism). Interestingly, glucose also increases with TSH primarily below the median TSH, diastolic blood pressure shows similar changes across the entire TSH range, whereas body mass index, triglycerides, and high-density lipoprotein (HDL)-cholesterol change only at the highest normal TSH values, which are associated with lower free T4 concentration.
  
  
  CONCLUSIONS
  TSH and free T4 within the normal range are associated with the metabolic syndrome. The sample half-below the TSH median (with probably higher functional thyroid status) exhibited better metabolic and cardiovascular profiles.
authors.affiliation: Clinical Research Department, Spanish National Center for Cardiovascular Research (CNIC), Madrid, Spain; Department of Preventive Medicine and Public Health, School of Medicine, Universidad Autonoma de Madrid, Madrid, Spain; Department of Epidemiology, St. Louis University, St Louis, MO, USA. Electronic address: mlaclaustra@cnic.es.
authors.forename: M
authors.initials: M
authors.lastname: Laclaustra
authors.affiliation: Clinical Research Department, Spanish National Center for Cardiovascular Research (CNIC), Madrid, Spain.
authors.forename: Y
authors.initials: Y
authors.lastname: Hurtado-Roca
authors.affiliation: Clinical Research Department, Spanish National Center for Cardiovascular Research (CNIC), Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Sendin
authors.affiliation: Instituto de Investigación Sanitaria Aragón, Zaragoza, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Leon
authors.affiliation: Instituto de Investigación Sanitaria Aragón, Zaragoza, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Ledesma
authors.affiliation: Instituto de Investigación 12 de Octubre, CIBER-Epidemiología y Salud Pública, Madrid, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Andres
authors.affiliation: Clinical Research Department, Spanish National Center for Cardiovascular Research (CNIC), Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Fernandez-Ortiz
authors.affiliation: Department of Epidemiology, and Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; Department of Medicine, and Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
authors.forename: E
authors.initials: E
authors.lastname: Guallar
authors.affiliation: Clinical Research Department, Spanish National Center for Cardiovascular Research (CNIC), Madrid, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Ordovas
authors.affiliation: Instituto de Investigación Sanitaria Aragón, Zaragoza, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Casasnovas
mesh_terms: D000328:Adult; D000367:Age Factors; D001786:Blood Glucose / Q000032:analysis*; D001795:Blood Pressure Determination; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000503:physiopathology; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D006801:Humans; D015994:Incidence; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood* / Q000453:epidemiology* / Q000503:physiopathology; D008875:Middle Aged; D015999:Multivariate Analysis; D011379:Prognosis; D018570:Risk Assessment; D012720:Severity of Illness Index; D013030:Spain / Q000453:epidemiology; D013972:Thyrotropin / Q000097:blood*
chemical_list: D001786:Blood Glucose; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D013972:Thyrotropin
keywords: Cardiovascular risk factors; Male; Metabolic syndrome; TSH; Thyroid