(15.09) Elevated Thyroglobulin Antibodies Following Intravenous Immunoglobulin Therapy in Thyroid Cancer

Thyroglobulin (TG), a protein produced by the thyroid gland, serves as a tumor marker in athyreotic differentiated thyroid cancer management, as per the American Thyroid Association. Accurate measurement of TG is crucial, requiring concurrent thyroglobulin antibodies (TgAb) monitoring. This case illustrates an unusual elevation in TgAb levels following intravenous immunoglobulin (IVIG) therapy, independent of cancer progression.

Case(s) Description :

We report a 77-year-old female with a history of papillary thyroid cancer, post right hemithyroidectomy, stable on levothyroxine. A surprising increase in TgAb levels, initially suggestive of cancer recurrence, was observed. However, a neck ultrasound showed no residual thyroid tissue. The elevation coincided with the patient's commencement of IVIG for chronic inflammatory demyelinating polyneuropathy (CIDP). The TgAb levels fluctuated corresponding to the IVIG treatment, eventually decreasing spontaneously without further intervention.

This case underscores the significance of considering external factors, such as IVIG treatment, in interpreting thyroid antibody levels. The temporal association between TgAb levels and IVIG therapy indicates an interaction unrelated to cancer activity.

 

Discussion :

Recognizing IVIG therapy as a potential confounder in TgAb testing is vital. Awareness of such interactions can prevent unnecessary interventions, reduce patient's anxiety, and ensure accurate clinical decision-making in thyroid cancer follow-up.