title: The relationship between circulating estradiol and thyroid autoimmunity in males.
abstract: BACKGROUND
  Although autoimmune thyroid disease is less common in males, it is unclear whether estrogen contributes to the difference in susceptibility among males.
  
  
  OBJECTIVE
  To examine whether circulating estradiol (E₂) is related to thyroid autoimmunity in males.
  
  
  METHODS
  One-thousand two-hundred and sixty-three males aged 15-94 years were studied. Serum levels of E₂, TSH receptor antibody (TRAb), thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), free thyroxine (FT₄), and TSH were measured by ELISA.
  
  
  RESULTS
  Circulating E₂ varied widely in males, ranging 18.4-403.7 pmol/l with a mean value of 136.2±51.7 pmol/l. E₂ increased with age (r=0.18, P<0.001). No relationship between E₂ and BMI was found. When comparing the difference in E₂ according to the test results of TRAb, TPOAb, and TgAb, it was found that E₂ was significantly higher in subjects with positive TRAb (TRAb positive, E₂=170.3±59.8 pmol/l; TRAb negative, E₂=134.0±50.6 pmol/l; P<0.001). No difference in E₂ was demonstrated according to the results of TPOAb or TgAb. Logistic regression analysis showed that E₂ was a determinant of positive TRAb, independent of age and BMI. There was no relationship between serum E₂ and TSH or FT₄. However, E₂ was negatively related to TSH (r=-0.45, P<0.01) in subjects whose TSH levels fell below the reference range (0.3-4.2 mIU/l).
  
  
  CONCLUSIONS
  Higher circulating E₂ is related to thyroid autoimmunity in males as reflected by positive TRAb.
authors.affiliation: Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine.
authors.forename: La-or
authors.initials: LO
authors.lastname: Chailurkit
authors.forename: Wichai
authors.initials: W
authors.lastname: Aekplakorn
authors.forename: Boonsong
authors.initials: B
authors.lastname: Ongphiphadhanakul
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001323:Autoantibodies / Q000032:analysis; D015551:Autoimmunity; D004958:Estradiol / Q000097:blood*; D006306:Health Surveys; D006801:Humans; D018828:Immunoglobulins, Thyroid-Stimulating / Q000032:analysis*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D013785:Thailand; D013961:Thyroid Gland / Q000276:immunology* / Q000378:metabolism; D013967:Thyroiditis, Autoimmune / Q000097:blood* / Q000276:immunology / Q000503:physiopathology; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism; D013974:Thyroxine / Q000097:blood / Q000378:metabolism; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D018828:Immunoglobulins, Thyroid-Stimulating; C006606:anti-thyroglobulin; C056626:thyroid microsomal antibodies; C094372:thyrotropin-binding inhibitory immunoglobulin; D004958:Estradiol; D013972:Thyrotropin; D013974:Thyroxine