title: The Prevalence, Incidence and Natural Course of Positive Antithyroperoxidase Antibodies in a Population-Based Study: Tehran Thyroid Study.
abstract: OBJECTIVE
  Thyroid peroxidase antibody (TPOAb), the most common antibody frequently measured in population surveys is a protein expressed in the thyroid gland. We conducted the present study to analyze the prevalence and incidence of thyroid auto immunity and natural course of TPOAb in a population based study.
  
  
  METHODS
  This prospective study was conducted within the framework of the Tehran Thyroid Study (TTS) on 5783 (2376 men and 3407 women) individuals aged ≥ 20 years who had thyroid function tests at baseline and were followed up for median 9.1 year with TPOAb measurements at approximately every 3 years.
  
  
  RESULTS
  The mean age of total population at baseline was 40.04±14.32. At baseline, of the 5783 participants, 742 (12.8%) were TPOAb positive, with higher prevalence among women than in men (16.0 vs. 8.5%, p = 0.001). The prevalence of TPOAb positivity in the total population was 11.9, 14.9 and 13.6% in the young, middle age and elderly respectively. The total incidence rate (95%CI) of TPOAb positivity in the total population (5020) was 7.1 (6.36-7.98) per 1000 person-years of follow-up, with higher incidence of TPOAb positivity among young participants, i.e. 8.5 (7.5-9.7) per 1000 person-years. Sex specific incidence rate demonstrated that TPOAb positivity was higher in women, 9.3 (8.2-10.7) per 1000 person-years. The Cox's proportional hazard model analysis showed that the hazard ratio of developing TPOAb positivity was higher in women than men (P<0.0001) and tended to increase slightly with serum TSH levels (P<0.0001) but declined with increasing age (P<0.0001) in the total population. Our findings demonstrate that individuals, who became TPOAb positive in each phase, had significant elevation of TSH levels at the phase of seroconversion, compared to baseline values.
  
  
  CONCLUSIONS
  Gender, age and elevated serum TSH were found to be risk factors for developing TPOAb positivity. Furthermore, compared to baseline a significant elevation of TSH levels during seroconversion phase was observed in TPOAb positive individuals.
authors.affiliation: Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, I. R. Iran.
authors.forename: Atieh
authors.initials: A
authors.lastname: Amouzegar
authors.affiliation: Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, I. R. Iran.|Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, I.R. Iran.
authors.forename: Safoora
authors.initials: S
authors.lastname: Gharibzadeh
authors.affiliation: Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, I. R. Iran.
authors.forename: Elham
authors.initials: E
authors.lastname: Kazemian
authors.affiliation: Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, I. R. Iran.
authors.forename: Ladan
authors.initials: L
authors.lastname: Mehran
authors.affiliation: Prevention of Metabolic Disorders Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, I. R. Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Tohidi
authors.affiliation: Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, I. R. Iran.
authors.forename: Fereidoun
authors.initials: F
authors.lastname: Azizi
mesh_terms: D000328:Adult; D000906:Antibodies / Q000276:immunology*; D015551:Autoimmunity; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000276:immunology; D007037:Hypothyroidism / Q000097:blood / Q000276:immunology; D015994:Incidence; D007453:Iodide Peroxidase / Q000276:immunology*; D007492:Iran; D008297:Male; D015995:Prevalence; D016016:Proportional Hazards Models; D018570:Risk Assessment; D013961:Thyroid Gland / Q000276:immunology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood
chemical_list: D000906:Antibodies; D013972:Thyrotropin; D007453:Iodide Peroxidase; D013974:Thyroxine