title: Aggregation of thyroid autoantibodies in twins from opposite-sex pairs suggests that microchimerism may play a role in the early stages of thyroid autoimmunity.
abstract: BACKGROUND
  Microchimerism is the presence of small populations of cells from one individual in another genetically distinct individual. This phenomenon can arise from pregnancy, blood transfusion, or bidirectional cell trafficking between twins in utero. Microchimerism has recently been proposed to play a role in the pathogenesis of thyroid autoimmunity. In that case, twins from opposite-sex pairs (OS) should have an increased risk of thyroid autoantibodies (TA).
  
  
  OBJECTIVE
  The aim of the study was to compare the frequency of TA in twin individuals from OS and monozygotic (MZ) twin pairs.
  
  
  METHODS
  This was a case-control study of 240 individuals (120 females and 120 males) from OS twin pairs (cases) and 568 control individuals from MZ pairs (284 females and 284 males).
  
  
  METHODS
  Antibodies toward thyroid peroxidase (TPOAb), thyroglobulin (TgAb), and the TSH receptor (TSHRAb) were measured and considered positive if greater than 60 U/ml, greater than 60 U/ml, and greater than 1.0 U/liter, respectively.
  
  
  RESULTS
  The frequency of TPOAb, TgAb, and TSHRAb among female cases was 15.0, 5.0, and 4.2%, respectively, which was higher than the corresponding prevalences in the female control population: 7.4% (P = 0.018), 1.1% (P = 0.023), and 0.7% (P = 0.026), respectively. However, when corrected for the number of phenotypes studied (TPOAb, TgAb, TSHRAb, and any thyroid antibody), the association remained significant only in the combined group, P(corrected) = 0.012. Essentially similar results were obtained in males.
  
  
  CONCLUSIONS
  Both female and male twins from OS pairs, as opposed to MZ pairs, have an increased frequency of TA, indicating a potential role of microchimerism in developing TA.
authors.affiliation: Department of Endocrinology and Metabolism, Odense University Hospital, 5000 Odense C, Denmark. thomas.brix@ouh
authors.forename: Thomas Heiberg
authors.initials: TH
authors.lastname: Brix
authors.forename: Pia Skov
authors.initials: PS
authors.lastname: Hansen
authors.forename: Kirsten Ohm
authors.initials: KO
authors.lastname: Kyvik
authors.forename: Laszlo
authors.initials: L
authors.lastname: Hegedüs
mesh_terms: D000293:Adolescent; D000328:Adult; D001323:Autoantibodies / Q000097:blood; D015551:Autoimmunity; D001724:Birth Weight; D046528:Chimerism / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007453:Iodide Peroxidase / Q000276:immunology; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D011989:Receptors, Thyrotropin / Q000276:immunology; D013954:Thyroglobulin / Q000276:immunology; D013961:Thyroid Gland / Q000276:immunology*; D014429:Twins, Dizygotic / Q000235:genetics* / Q000276:immunology; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D011989:Receptors, Thyrotropin; D013954:Thyroglobulin; D007453:Iodide Peroxidase