en Endocrinology Endocrinology Original Article Original Article <span style="font-size:14px;"><span style="font-family:Times New Roman;"><span style="line-height:13.7pt"><b><i><span style="color:blue">Background</span></i></b><i><span style="color:blue">:</span></i> Differentiated thyroid carcinoma (DTC) comprises nearly 90% of all thyroid malignancies. The main focus of our study was to examine how measuring Tg at multiple time points could predict the persistence and/or recurrence of both local and distant diseases.</span><br> <span style="line-height:13.7pt"><b><i><span style="color:blue">Methods:</span></i></b> In this retrospective, single-center, observational study, we examined records of all patients who underwent total thyroidectomy for DTC and received radioactive iodine (RAI) ablation/therapy at the Nuclear Medicine of Shahid Beheshti Hospital. Blood samples were collected at two time, approximately 30 days before RAI (Tg-30 and TSH-30) and the same day of RAI, after TSH-stimulation (Tg-0 and TSH-0). During the follow-up period, patients were categorized into the four groups according to the ATA guideline. Group with an excellent response (ER), nodal disease (ND), distant disease (DD) and partial response (PR). </span><br> <span style="line-height:13.7pt"><b><i><span style="color:blue">Results:</span></i></b> A significant difference between Tg-0 and Tg-30 was observed only in the ER group and the other 3 groups (p<0.001), and no significant difference was observed between the remaining 3 groups (p>0.05). Cut-off point of 1.35 ng/mL for the Tg-30 and 4.7 ng/mL for the Tg-0 was used with best sensitivity and specificity for differentiation of ER vs. ND. A cut-off point of 14.25 ng/mL for the Tg-30 and 40 ng/mL for the Tg-0 was able to correctly identify ER vs. DD. </span><br> <span style="line-height:13.7pt"><b><i><span style="color:blue">Conclusion</span></i></b><i><span style="color:blue">:</span></i> By using the cut-off values obtained in this study, it is possible to more accurately predict local or distant recurrences. Maybe these patients need a shorter follow-up period that leads to more appropriate treatment decisions.</span></span></span><br> &nbsp; Differentiated Thyroid Carcinoma, Serum Thyroglobulin, Radioactive Iodine Therapy, Thyroid Remnant Ablation 718 724 http://caspjim.com/browse.php?a_code=A-10-2269-3&slc_lang=en&sid=1 Amir Gholami amir_gholami_4@yahoo.com 100319475328460054644 100319475328460054644 No Department of Radiology, School of Medicine, Babol University of Medical Sciences, Babol, Iran Seyyed Ali Hosseini ali.hosseini6922@gmail.com 100319475328460054645 0009-0009-2000-247X No Student Research Committee, Babol University of Medical Sciences, Babol, Iran Hemmat Gholinia h_gholinia@yahoo.com 100319475328460054646 100319475328460054646 No Health Research Institute, Babol University of Medical Sciences, Babol, Iran. Seyyed Hossein Mousavie Anijdan shmosavia@gmail.com 100319475328460054647 100319475328460054647 Yes Department of Radiology, School of Medicine, Babol University of Medical Sciences, Babol, Iran