title: Antithyroid antibodies and parity: further evidence for microchimerism in autoimmune thyroid disease.
abstract: OBJECTIVE
  Fetal microchimerism may have a role in development of autoimmune thyroid disorders. Using parity as a surrogate for increasing fetal cell exposure, we analyzed its association with thyroid peroxidase antibody levels.
  
  
  METHODS
  Secondary analysis of serum thyroid analytes determined in 17,298 women from a population-based prospective study between 2001 and 2003. Sera were assayed for thyrotropin, free thyroxine, and antithyroid peroxidase antibodies. We analyzed the relationship between thyroid peroxidase antibodies and increasing parity.
  
  
  RESULTS
  The incidence of abnormally elevated thyroid peroxidase antibody levels (>50 IU/mL) increased with advancing parity, but was not significant after adjustment for maternal characteristics. However, at higher thyroid peroxidase antibody levels (>500 IU/mL), a significant relationship with advancing parity persisted after adjustments (P = .002).
  
  
  CONCLUSIONS
  Advancing parity is associated with an increased risk for high serum concentrations of antithyroid peroxidase antibodies. This suggests fetal microchimerism may play a role in development of autoimmune thyroid disorders.
authors.affiliation: Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Laura G
authors.initials: LG
authors.lastname: Greer
authors.forename: Brian M
authors.initials: BM
authors.lastname: Casey
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Halvorson
authors.forename: Catherine Y
authors.initials: CY
authors.lastname: Spong
authors.forename: Donald D
authors.initials: DD
authors.lastname: McIntire
authors.forename: F Gary
authors.initials: FG
authors.lastname: Cunningham
mesh_terms: D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D046528:Chimerism; D005260:Female; D006801:Humans; D007453:Iodide Peroxidase / Q000097:blood / Q000276:immunology*; D010298:Parity; D011247:Pregnancy; D011446:Prospective Studies; D013960:Thyroid Function Tests; D013963:Thyroid Hormones / Q000097:blood; D013967:Thyroiditis, Autoimmune / Q000097:blood / Q000235:genetics* / Q000276:immunology
chemical_list: D001323:Autoantibodies; D013963:Thyroid Hormones; C056626:thyroid microsomal antibodies; D007453:Iodide Peroxidase