The relationship between circulating estradiol and thyroid autoimmunity in males
IntroductionAlthough autoimmune thyroid disease is less common in males, it is unclear whether estrogen contributes to the difference in susceptibility among males.ObjectiveTo examine whether circulating estradiol (E2) is related to thyroid autoimmunity in males.Patients and methodsOne-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.ResultsCirculating E2varied widely in males, ranging 18.4–403.7 pmol/l with a mean value of 136.2±51.7 pmol/l. E2increased with age (r=0.18,P<0.001). No relationship between E2and BMI was found. When comparing the difference in E2according to the test results of TRAb, TPOAb, and TgAb, it was found that E2was 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 E2was demonstrated according to the results of TPOAb or TgAb. Logistic regression analysis showed that E2was a determinant of positive TRAb, independent of age and BMI. There was no relationship between serum E2and TSH or FT4. However, E2was 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).ConclusionHigher circulating E2is related to thyroid autoimmunity in males as reflected by positive TRAb.