Significance of Prediagnostic Thyroid Antibodies in Women with Autoimmune Thyroid Disease

Introduction: Antibodies to thyroglobulin (Tg), thyroperoxidase (TPO), and TSH receptor (TSH-R) are prevalent in autoimmune thyroid diseases. We aimed to assess whether females with Graves disease or Hashimoto thyroiditis are more likely than age-matched controls to have thyroid antibodies before clinical diagnosis and to measure the timing of antibody seroconversion. Methods: This was a nested case-control study using the Department of Defense Serum Repository and the Defense Medical Surveillance System, 1998-2007. We assessed thyroid antibodies in the serum of 522 female, active-duty, military personnel including: 87 Graves disease cases, 87 Hashimoto thyroiditis cases, and 348 age matched controls. One serum sample was available at the time of the clinical diagnosis (+/- 6 months); three additional samples were retrieved from the repository up to 7 yr before the clinical diagnosis, for a total of 2088 samples. Results: In Hashimoto thyroiditis, TPO antibodies were found in about 66% of the cases at all time points. Tg antibodies showed a similar stationary trend, at a lower prevalence of about 53% at all time points. No TSH-R antibodies were found. In Graves disease, TPO antibodies gradually increased from 31% at 5-7 yr priortodiagnosisto57% at diagnosis and Tg antibodies from 18 to 47%. TSH-R antibodies were present before diagnosis and showed an increasing prevalence from 2, 7, 20, to 55%. Conclusions: Antibodies to Tg, TPO, and TSH-R precede by years the development of the diagnostic autoimmune thyroid diseases phenotype. Overall, the presence of thyroid antibodies in apparently healthy individuals should not be neglected. (J Clin Endocrinol Metab 96: E1466-E1471, 2011)