title: Characterization of subclinical thyroid dysfunction from cardiovascular and metabolic viewpoints: the Suita study.
abstract: BACKGROUND
  Subclinical hypothyroidism, defined as high serum thyroid-stimulating hormone (TSH) levels and normal serum free-triiodothyronine (fT3) and serum free-thyroxine (fT4) levels, is a common medical problem among the elderly, but it is unclear whether it should be treated with thyroid hormone replacement therapy.
  
  
  RESULTS
  A cross-sectional study of 3,607 participants in a community health survey in Suita, in the northern part of Osaka, was performed. Participants were categorized into 5 groups: normal, hyperthyroidism, hypothyroidism, subclinical hypothyroidism, and subclinical hyperthyroidism. The association between each group and various phenotypes was examined, in relation to cardiovascular disease and metabolic syndromes. Serum TSH levels increased and fT3 and fT4 levels decreased with age. A total of 14.6% of subjects aged 70-80 years and 20.1% of subjects aged older than 80 years were classified as having subclinical hypothyroidism. Subclinical hypothyroidism was not associated with glycol-hemoglobin A1c, body mass index, pulse rate, hypertension, total cholesterol, high-density lipoprotein cholesterol or triglyceride levels or intima-media thickness. It was only associated with higher fasting blood glucose and glycol-hemoglobin A1c levels compared with euthyroidism.
  
  
  CONCLUSIONS
  The present observation does not support the need for treatment of subclinical hypothyroidism or subclinical hyperthyroidism.
authors.affiliation: Department of Epidemiology, National Cardiovascular Center, Suita, Japan. ntaka@ri.ncvc.go.jp
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Takashima
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Niwa
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Mannami
authors.forename: Hitonobu
authors.initials: H
authors.lastname: Tomoike
authors.forename: Naoharu
authors.initials: N
authors.lastname: Iwai
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001786:Blood Glucose / Q000378:metabolism; D002319:Cardiovascular System / Q000378:metabolism* / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D020249:Hormone Replacement Therapy; D006801:Humans; D006980:Hyperthyroidism / Q000378:metabolism / Q000503:physiopathology; D007037:Hypothyroidism / Q000378:metabolism / Q000503:physiopathology; D007564:Japan; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D013959:Thyroid Diseases / Q000378:metabolism* / Q000503:physiopathology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; D013972:Thyrotropin; D013974:Thyroxine; D014284:Triiodothyronine