Context: Circulating thyroglobulin antibodies (TgAb) can confound measurement of serum thyroglobulin and impair thyroid cancer surveillance. Few data exist on the significance of TgAb in pediatric thyroid cancer.Objective: To describe the prevalence, natural history, and clinical significance of TgAb in children with thyroid cancer.Design: Retrospective cohort study.Setting: Single academic pediatric center.Patients: Seventy-three consecutive children (#18 years) with nonmedullary thyroid cancer who had serum TgAb measured within 6 months after diagnosis.Main Outcome Measures: Prevalence and natural history of TgAb; association of TgAb status and resolution with patient and disease characteristics.Results: TgAb were detected in 41% of subjects (30 of 73) and were associated with lymph node metastasis (83% vs 53%, P = 0.01) but not distant metastasis. In patients with TgAb, resolution occurred in 44% (11 of 25) over a median follow-up of 3.8 years. Median time to clear TgAb was 10.7 months, and 10 of 11 patients who cleared (91%) did so within 2 years. Resolution of TgAb was associated with lower initial TgAb level (median 4.5 vs 76 normalized units, P = 0.003). TgAb positivity at diagnosis was not independently associated with persistent or recurrent disease (odds ratio 3.20, 95% confidence interval 0.95 to 10.80, P = 0.06).Conclusions: TgAb are common at diagnosis in children with thyroid cancer but resolve in nearly half of patients within 1 to 2 years. TgAb are associated with the presence of lymph node metastasis at diagnosis, but the long-term prognostic significance remains to be determined. (J Clin Endocrinol Metab 102: [3146][3147][3148][3149][3150][3151][3152][3153] 2017) T hyroid cancer is the most common endocrine malignancy in both children and adults. Although the risk of mortality from thyroid cancer is low, lifelong surveillance is mandatory due to the risk of disease recurrence, which may occur many years after initial treatment and apparent cure. This issue is especially salient in children with thyroid cancer because of the decades of monitoring required.Because many differentiated thyroid cancers produce thyroglobulin (Tg), measurement of serum Tg can detect thyroid cancer recurrence or progression and is therefore an important element of long-term surveillance in patients with thyroid cancer (1). However, circulating Tg antibodies (TgAb) can confound conventional Tg assays and thereby prevent accurate measurement of Tg levels (2, 3). TgAb therefore represent a significant clinical issue Abbreviations: NED, no evidence of disease; OR, odds ratio; RAI, radioactive iodine; Tg, thyroglobulin; TgAb, Tg antibody.
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