title: Subclinical thyroid dysfunction as a risk factor for cardiovascular disease.
abstract: BACKGROUND
  There have been few large epidemiological studies examining the association between thyroid dysfunction and cardiovascular disease. In particular, it is uncertain if subclinical hypothyroidism is a risk factor for cardiovascular disease.
  
  
  METHODS
  Serum thyrotropin and free thyroxine concentrations were measured in 2108 archived serum samples from a 1981 community health survey in Busselton, Western Australia (Busselton Health Study). In a cross-sectional study, we examined the prevalence of coronary heart disease in subjects with and without subclinical thyroid dysfunction. In a longitudinal study, we examined the risk of cardiovascular mortality and coronary heart disease events (fatal and nonfatal combined) to the end of 2001 (excluding subjects who had coronary heart disease at baseline).
  
  
  RESULTS
  In the cross-sectional analysis, subjects with subclinical hypothyroidism (n = 119) had a significantly higher prevalence of coronary heart disease than euthyroid subjects (n = 1906) (age- and sex-adjusted prevalence odds ratio, 1.8; 95% confidence interval, 1.0-3.1; P = .04). In the longitudinal analysis of subjects with subclinical hypothyroidism (n = 101), there were 21 cardiovascular deaths observed compared with 9.5 expected (age- and sex-adjusted hazard ratio, 1.5; 95% confidence interval, 1.0-2.4; P = .08) and 33 coronary heart disease events observed compared with 14.7 expected (age- and sex-adjusted hazard ratio, 1.7; 95% confidence interval, 1.2-2.4; P < .01). The increased risk of coronary heart disease events remained significant after further adjustment for standard cardiovascular risk factors. Subjects with subclinical hyperthyroidism (n = 39) had no adverse outcomes.
  
  
  CONCLUSIONS
  Subclinical hypothyroidism may be an independent risk factor for coronary heart disease.
authors.affiliation: Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia. john.walsh@health.wa.gov.au
authors.forename: John P
authors.initials: JP
authors.lastname: Walsh
authors.forename: Alexandra P
authors.initials: AP
authors.lastname: Bremner
authors.forename: Max K
authors.initials: MK
authors.lastname: Bulsara
authors.forename: Peter
authors.initials: P
authors.lastname: O'Leary
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Leedman
authors.forename: Peter
authors.initials: P
authors.lastname: Feddema
authors.forename: Valdo
authors.initials: V
authors.lastname: Michelangeli
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D016001:Confidence Intervals; D003327:Coronary Disease / Q000453:epidemiology / Q000209:etiology*; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000150:complications*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors; D017678:Sex Distribution; D015996:Survival Rate; D013972:Thyrotropin / Q000097:blood; D014904:Western Australia / Q000453:epidemiology
chemical_list: D013972:Thyrotropin