title: The TSH levels and risk of hypothyroidism: Results from a population based prospective cohort study in an Iranian adult's population.
abstract: OBJECTIVE
  The aim of current study was to assess the relationship between serum TSH levels and hypothyroidism risk in the euthyroid population.
  
  
  METHODS
  In a population-based cohort study, a total of 615 individuals with a normal baseline TSH, from of total population (n=2254) in 2006, were followed up for 6years. TSH, total T4, thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb) were measured. The relative risk (RR) and 95% confidence interval (95%CI) were calculated based on logistic regression. The Receiver Operating Characteristic (ROC) analysis along with area under the curve (AUC) was used to prediction of future hypothyroidism.
  
  
  RESULTS
  TSH level in 2006 was a significant predictor for overt hypothyroidism, in the total population (RR=3.5) and female (RR=1.37) (all, P value<0.05). A cutoff value of TSH at 2.05mIU/L [AUC: (CI95 %), 0.68 (0.44-0.92; P=0.05)] was obtained for differentiating the patients with overt hypothyroidism from euthyroid. However, this cut off was not observed when we included only negative TPO and TgAbs people in 2006. The RR of hypothyroidism increased gradually when TSH level increased from 2.06-3.6mIU/L to >3.6mIU/L in the total population and both sexes. In women, the risk of overt hypothyroidism was significantly higher in subjects with TSH above 3.6 than those subject with THS levels≤2.05 [RR: (CI95 %), 20.57(2.-207.04), P value<0.05].
  
  
  CONCLUSIONS
  A cutoff value of TSH at 2.05mIU/L could predict the development of overt hypothyroidism in future. However, it was not applicable for people with negative TPOAb and negative TgAb.
authors.affiliation: Isfahan Endocrine and Metabolism Research Center, Isfahan University of Medical Sciences, Isfahan, Iran. Electronic address: aminorroaya@med.mui.ac.ir.
authors.forename: Ashraf
authors.initials: A
authors.lastname: Aminorroaya
authors.affiliation: Isfahan Endocrine and Metabolism Research Center, Isfahan University of Medical Sciences, Isfahan, Iran. Electronic address: meamar@pharm.mui.ac.ir.
authors.forename: Rokhsareh
authors.initials: R
authors.lastname: Meamar
authors.affiliation: Isfahan Endocrine and Metabolism Research Center, Isfahan University of Medical Sciences, Isfahan, Iran. Electronic address: m_amini@med.mui.ac.ir.
authors.forename: Massoud
authors.initials: M
authors.lastname: Amini
authors.affiliation: Isfahan Endocrine and Metabolism Research Center, Isfahan University of Medical Sciences, Isfahan, Iran; Department of Biostatistics and Epidemiology, School of Public Health, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Awat
authors.initials: A
authors.lastname: Feizi
authors.affiliation: Central London Community Health Trust, UK.
authors.forename: Maryam
authors.initials: M
authors.lastname: Nasri
authors.affiliation: Isfahan Endocrine and Metabolism Research Center, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Azamosadat
authors.initials: A
authors.lastname: Tabatabaei
authors.affiliation: Isfahan Endocrine and Metabolism Research Center, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Elham
authors.initials: E
authors.lastname: Faghihimani
mesh_terms: D000328:Adult; D019540:Area Under Curve; D001323:Autoantibodies / Q000097:blood*; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood* / Q000503:physiopathology; D007492:Iran; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012372:ROC Curve; D012306:Risk; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood*; D055815:Young Adult
chemical_list: D001323:Autoantibodies; C006606:anti-thyroglobulin; C056626:thyroid microsomal antibodies; D013972:Thyrotropin
keywords: Euthyroidism; Hypothyroidism; Risk; TSH