Analysis of pre-ablative and preoperative thyroglobulin in differentiated thyroid cancerBackground: The measurement of plasma thyroglobulin (Tg) is widely used in the monitoring of differentiated thyroid cancer (CDT). In recent years, its value as a prognostic marker prior to ablation with radioiodine has increased, demonstrating its high negative predictive value. Recent studies indicate that a wide variety of factors could potentially influence pre-ablative Tg values, including residual tumor burden and stimulation modality. Aim: To relate the value of pre-ablative Tg with the amount of preoperative disease burden, lymph node metastases, treatment, and presence of residual disease. Material and Methods: Retrospective observational study of 70 patients with CDT treated between 2012 and 2018. The amount of disease burden was defined as the sum of largest diameter of individual tumors in each patient, and as the individually largest tumor per patient and number of metastatic lymph nodes. Results: A smaller tumor size and absence of remnant tissue was associated with lower Tg values, although the association was not always significant. Furthermore, no significant difference was found between Tg levels measured within or more than 14 days after the surgical procedure. Thus, an early measurement of pTg after surgery would allow an initial therapeutic decision making. Conclusions: A statistical association between pre-ablative Tg levels and the amount of preoperative tumor tissue burden was found in some subgroups of patients.