title: Subclinical hypothyroidism and mortality in a large Austrian cohort: a possible impact on treatment?
abstract: BACKGROUND
  Clinical implications of subclinical hypothyroidism (SCH) are still matter of intense debate, resulting in the controversial discussion whether subclinical hypothyroidism should be treated. We performed a cohort study to evaluate the impact of subclinical hypothyroidism on vascular and overall mortality.
  
  
  METHODS
  Between 02/1993 and 03/2004, a total of 103,135 persons attending the General Hospital Vienna with baseline serum thyrotropin (TSH, thyroid-stimulating hormone) and free thyroxin (fT4) measurements could be enrolled in a retrospective cohort study. Subclinical hypothyroidism was defined by elevated TSH ranging from 4.5 to 20.0 mIU/L and normal fT4 concentration (0.7-1.7 ng/dL). Overall and vascular mortality as primary endpoints were assessed via record linkage with the Austrian Death Registry.
  
  
  RESULTS
  A total of 80,490 subjects fulfilled inclusion criteria of whom 3934 participants (3.7%) were classified as SCH (868 males and 3066 females, median age 48 years). The mean follow-up among the 80,490 subjects was 4.1 years yielding an observation period of 373,301 person-years at risk. In a multivariate Cox regression model adjusted for age and gender TSH levels showed a dose-dependent association with all-cause mortality. The association between SCH and overall or vascular mortality was stronger in men below 60 years compared to older males or females.
  
  
  CONCLUSIONS
  Our data support the hypothesis that SCH might represent an independent risk factor for overall and vascular mortality, especially in men below 60 years. Whether this group would benefit from replacement therapy should be evaluated in interventional studies.
authors.affiliation: Department for Trauma Surgery, Medical University of Vienna, Vienna, Austria.
authors.forename: Florian Maria
authors.initials: FM
authors.lastname: Kovar
authors.affiliation: Central Laboratory, Wilhelminenspital der Stadt Wien, Vienna, Austria.
authors.forename: I-Fei
authors.initials: IF
authors.lastname: Fang
authors.affiliation: Department of Medical and Chemical Laboratory Diagnostics, Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Vienna, AKH-Wien Waehringer Guertel 18-20, 1090, Vienna, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Perkmann
authors.affiliation: Department of Medical and Chemical Laboratory Diagnostics, Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Vienna, AKH-Wien Waehringer Guertel 18-20, 1090, Vienna, Austria.
authors.forename: Helmuth
authors.initials: H
authors.lastname: Haslacher
authors.affiliation: Central Laboratory, Wilhelminenspital der Stadt Wien, Vienna, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Slavka
authors.affiliation: Department of Medical and Chemical Laboratory Diagnostics, Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Vienna, AKH-Wien Waehringer Guertel 18-20, 1090, Vienna, Austria.|Central Laboratory, Kaiser Franz Josef-Spital der Stadt Wien, Vienna, Austria.
authors.forename: Manuela
authors.initials: M
authors.lastname: Födinger
authors.affiliation: Department of Medical and Chemical Laboratory Diagnostics, Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Vienna, AKH-Wien Waehringer Guertel 18-20, 1090, Vienna, Austria.|Labors.at, Vienna, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Endler
authors.affiliation: Department of Medical and Chemical Laboratory Diagnostics, Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Vienna, AKH-Wien Waehringer Guertel 18-20, 1090, Vienna, Austria. oswald.wagner@meduniwien.ac.at.
authors.forename: Oswald F
authors.initials: OF
authors.lastname: Wagner
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D058070:Asymptomatic Diseases / Q000401:mortality* / Q000628:therapy; D001317:Austria / Q000453:epidemiology; D002318:Cardiovascular Diseases / Q000401:mortality* / Q000517:prevention & control; D015331:Cohort Studies; D015897:Comorbidity; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000401:mortality* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D017678:Sex Distribution; D015996:Survival Rate
keywords: All-cause mortality; All-cause vascular mortality; Subclinical hypothyroidism