title: Association of low baseline free thyroxin levels with progression of coronary artery calcification over 4 years in euthyroid subjects: the Kangbuk Samsung Health Study.
abstract: Overt and subclinical hypothyroidism are risk factors for atherosclerosis and cardiovascular diseases. It is unclear whether thyroid hormone levels within the normal range are also associated with atherosclerosis measured by coronary artery calcium (CAC).
  
  
  
  This study aimed to examine the relationship between normal variations in thyroid function and changes in CAC.
  
  
  
  We conducted a 4-year retrospective study of 2173 apparently healthy men and women with normal thyroid hormone levels. Their free thyroxin (FT4), free triiodothyronin (FT3) and thyroid-stimulating hormone (TSH) levels were measured by electrochemiluminescent immunoassay. The CAC score (CACS) of each subject was measured by multidetector computed tomography in both 2010 and 2014. Progression of CAC was defined as a CACS change over 4 years > 0.
  
  
  
  The mean CACS changes over 4 years by quartiles of baseline FT4 level (lowest to highest) were 12·9, 8·43, 7·82 and 7·81 (P = 0·028). CAC progression was not significantly associated with either the baseline FT3 or TSH levels. The odds ratios (OR) for CAC progression over 4 years (highest vs lowest quartile for baseline FT4) were 0·647 (95% confidence interval (CI) 0·472-0·886) after adjustment for confounding factor, which were attenuated with further adjustment for lipid profiles, homoeostasis model assessment of insulin resistance, high-sensitivity C-reactive protein and hypertension [0·747 (95% CI 0·537-1·038)]. Quartiles of baseline FT3 or TSH level did not show any increased OR for CAC progression after adjustment for confounding factors.
  
  
  
  In this cohort of euthyroid men and women, a low baseline FT4 level was associated with a high risk of CACS progression over 4 years.
authors.affiliation: Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Hye-Jeong
authors.initials: HJ
authors.lastname: Park
authors.affiliation: Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Jihyun
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Eun Jin
authors.initials: EJ
authors.lastname: Han
authors.affiliation: Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Se Eun
authors.initials: SE
authors.lastname: Park
authors.affiliation: Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Cheol-Young
authors.initials: CY
authors.lastname: Park
authors.affiliation: Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Won-Young
authors.initials: WY
authors.lastname: Lee
authors.affiliation: Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Ki-Won
authors.initials: KW
authors.lastname: Oh
authors.affiliation: Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Sung-Woo
authors.initials: SW
authors.lastname: Park
authors.affiliation: Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Rhee
mesh_terms: D000328:Adult; D000368:Aged; D003324:Coronary Artery Disease / Q000378:metabolism*; D018450:Disease Progression; D005067:Euthyroid Sick Syndromes / Q000097:blood / Q000150:complications*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012189:Retrospective Studies; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood; D061205:Vascular Calcification / Q000175:diagnosis / Q000209:etiology*
chemical_list: D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine