A New Perspective on Anti-Thyroglobulin Antibody Patterns in the Follow-Up of Papillary Thyroid Carcinoma

Objective: This study aimed to describe distinct anti-thyroglobulin antibody (TgAb) trend trends and assess their association with clinical outcomes in papillary thyroid carcinoma (PTC). Methods: Twenty-two PTC patients with TgAb positivity (at diagnosis, postoperative follow-up, or post-Radioidoine (RAI) were retrospectively analyzed, classified into classical (declining/stable/ increasing) and nonclassical trend groups, and their clinical and outcome data was reviewed. Results: Classical TgAb patterns were observed in 14 patients (63.6%), including 12 with a declin ing pattern (median time to seronegativity: 20 months, range: 12-48) and 2 with persistently stable positivity. Among those with decreasing TgAb, 2 patients had previously experienced structural recurrence, both accompanied by transient TgAb rises. In the stable subgroup, 1 patient had per sistent but subcentimetric nodal disease without progression. Nonclassical patterns were identified in 8 patients (36.4%), distributed across 4 distinct scenarios: (1) Persistently very high TgAb remain ing undetectable without structural disease (n = 2), lasting ≥3 years, (2) transient de novo TgAb posi tivity following radioiodine treatment (RAIT) (n = 2), with spontaneous decline to negativity within 12-18 months, (3) late-onset de novo TgAb after RAIT, remaining stable without structural disease (n = 2), remaining stable (up to 5 years) without evidence of disease, (4) de novo TgAb rising with recurrence (n = 2), 1 presenting with nodal relapse and the other with pulmonary metastases, both showing TgAb decline after treatment. Conclusion: In PTC follow-up, TgAb trends were more informative than absolute levels: transient ele vations and de novo stable or persistently stable TgAb were less likely to indicate structural disease, whereas de novo rising TgAb strongly suggested recurrence. However, given the small, single-center cohort and retrospective design, these findings require confirmation in larger prospective studies. Cite this article as: Bahçecioğlu AB, Erdem M. A new perspective on anti thyroglobulin antibody patterns in the follow-up of papillary thyroid carcinoma. Endocrinol Res Pract. 2025;29(4):320-326.