Can TPO and Thyroglobulin Antibodies Be Seen in Graves' Disease?
Yes, both thyroid peroxidase (TPO) antibodies and thyroglobulin (Tg) antibodies are commonly present in patients with Graves' disease, though they are not the primary pathogenic antibodies.
Prevalence of These Antibodies in Graves' Disease
The presence of TPO and Tg antibodies in Graves' disease is well-documented:
TPO antibodies are present in approximately 70-80% of Graves' disease patients at diagnosis, with prevalence ranging from 57% to 80% depending on the study 1, 2, 3.
Thyroglobulin antibodies are found in 47-54% of Graves' disease patients at diagnosis 1, 2, 4.
These antibodies can be detected years before clinical diagnosis of Graves' disease, with TPO antibodies gradually increasing from 31% at 5-7 years prior to diagnosis to 57% at diagnosis, and Tg antibodies increasing from 18% to 47% over the same period 5.
Distinguishing Features from Hashimoto's Disease
While both conditions involve thyroid autoantibodies, there are important differences:
In Hashimoto's thyroiditis, TPO antibodies remain stationary at approximately 66% at all time points, and Tg antibodies remain at about 53%, showing a more consistent pattern 5.
In Graves' disease, these antibodies show a gradual increasing trend over time before diagnosis, suggesting a different pathophysiological evolution 5.
The primary pathogenic antibody in Graves' disease is the TSH receptor antibody (TRAb), which shows an increasing prevalence from 2% to 55% in the years leading up to diagnosis 5.
Clinical Significance and Limitations
TPO and Tg antibodies do not predict clinical outcomes in Graves' disease:
No significant association exists between TPO antibody levels and remission or relapse after antithyroid drug treatment 1.
The presence of TPO or Tg antibodies does not predict the final outcome of Graves' disease, including response to treatment or likelihood of sustained remission 2.
TgAb-positive patients at diagnosis have significantly less thyroid eye disease (TED) compared to TgAb-negative patients (15.1% versus 33.3%, P = 0.012), suggesting a potential protective effect 4.
Lower titers of TgAb at 18 months of treatment were associated with relapse, though this was the only predictive finding 4.
Common Pitfalls to Avoid
Do not confuse the presence of TPO/Tg antibodies with Hashimoto's disease when TRAb is also elevated and hyperthyroidism is present—this is Graves' disease with coexisting thyroid autoimmunity 6, 1.
Do not use TPO or Tg antibody levels to guide treatment decisions in Graves' disease, as they lack predictive value for remission or relapse 1, 2.
Remember that Tg antibodies can interfere with thyroglobulin measurement, which is more relevant in thyroid cancer monitoring than in Graves' disease management 7, 6.
Antithyroid drug treatment does not produce new thyroid hormone autoantibodies in Graves' disease patients who were previously negative 3.