The relationship between circulating estradiol and thyroid autoimmunity in males

Abstract

Introduction: 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. Patients and 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 E 2 was significantly higher in subjects with positive TRAb (TRAb positive, E2=170.3±59.8 pmol/l; TRAb negative, E 2=134.0±50.6 pmol/l; P<0.001). No difference in E 2 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). Conclusion: Higher circulating E2 is related to thyroid autoimmunity in males as reflected by positive TRAb. © 2014 European Society of Endocrinology.