title: Association between parity and autoimmune thyroiditis in a general female population.
abstract: BACKGROUND
  Autoimmune thyroid disease (AIT) is more common in females than in males. Furthermore, it is well documented that the risk of thyroid autoimmunity increases during pregnancy and in the postpartum period. The objective of the present study was to analyse the association between parity and AIT by using ultrasound and serological data.
  
  
  METHODS
  The study population included 2156 women, aged 20-79 years. Serum thyroperoxidase antibodies (anti-TPO) and thyrotropin levels were measured and thyroid ultrasonography was performed. AIT was defined according to the combined presence of a hypoechogenic thyroid pattern and positive anti-TPO levels (>200 IU/ml). Odds ratios (OR) and 95% confidence intervals (CI) were calculated.
  
  
  RESULTS
  The analyses revealed an association between parity and AIT. Women with at least one pregnancy had increased odds for AIT (OR 4.6 [95%-CI 1.4-15.1], p < 0.05) compared to women who have never been pregnant. Similar results were observed using hypoechogenic thyroid pattern (OR 1.7 [95%-CI 1.0-2.9], p < 0.05) and positive anti-TPO levels (OR 1.8 [95%-CI 1.0-3.3], p = 0.05) as separate dependent variables or using number of births as alternate independent variable.
  
  
  CONCLUSIONS
  In this female population we found an association between parity and AIT and conclude that parity appears to be a potential risk factor for AIT.
authors.affiliation: Institute of Community Medicine-Unit SHIP, Ernst Moritz Arndt University of Greifswald, Greifswald, Germany. nele.friedrich@uni-greifswald.de
authors.forename: Nele
authors.initials: N
authors.lastname: Friedrich
authors.forename: Sabine
authors.initials: S
authors.lastname: Schwarz
authors.forename: Jens
authors.initials: J
authors.lastname: Thonack
authors.forename: Ulrich
authors.initials: U
authors.lastname: John
authors.forename: Henri
authors.initials: H
authors.lastname: Wallaschofski
authors.forename: Henry
authors.initials: H
authors.lastname: Völzke
mesh_terms: D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood; D001324:Autoantigens / Q000276:immunology; D005260:Female; D006801:Humans; D007453:Iodide Peroxidase / Q000276:immunology; D033862:Iron-Binding Proteins / Q000276:immunology; D008875:Middle Aged; D010298:Parity; D011247:Pregnancy; D012306:Risk; D013961:Thyroid Gland / Q000000981:diagnostic imaging; D013967:Thyroiditis, Autoimmune / Q000209:etiology*; D013972:Thyrotropin / Q000097:blood; D014463:Ultrasonography
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D033862:Iron-Binding Proteins; D013972:Thyrotropin; C056658:TPO protein, human; D007453:Iodide Peroxidase