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> The cause of thyrotoxicosis can be determined through the thyroid uptake of 99mTc-pertechnetate<b>.</b> The goal of the study was to calculate the cut-off value of 99mTc-pertechnetate of the thyroid gland for the differential diagnosis of Graves&#39; disease from subacute thyroiditis.</span><br> <span style="line-height:13.7pt"><b><i><span style="color:blue">Methods:</span></i></b> A total of 60 patients were included in the study<b>.</b> Based on thyroid scan findings, 30 patients were in the Graves group and 30 of them had been diagnosed as subacute thyroiditis. Biochemical parameters, thyroid scintigraphy, and the percentage thyroidal 99mTc-pertechnetate uptake results were thoroughly assessed.</span><br> <span style="line-height:13.7pt"><b><i><span style="color:blue">Results:</span></i></b> The mean percentage 99mTc-pertechnetate uptake in Graves group was much higher than that of the subacute thyroiditis group, which was statistically significant (P <0.001). Receiver operating characteristic (ROC) analysis revealed that the uptake cut-off value of 1.1% had the sensitivity and specificity of 97% and 95%, respectively.</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> The findings depicted that the cutoff value of 1.1% for 99mTc-pertechnetate uptake could be a helpful index to differentiate Graves&#39; disease from subacute thyroiditis, especially when it is difficult to distinguish between the two diseases using conventional diagnostic methods. </span></span></span><br> &nbsp; Thyrotoxicosis, Technetium uptake, Graves' disease, Subacute thyroiditis, 513 518 http://caspjim.com/browse.php?a_code=A-10-2269-2&slc_lang=en&sid=1 Amir Gholami amir_gholami_4@yahoo.com 100319475328460053341 100319475328460053341 No Department of Radiology, School of Medicine, Babol University of Medical Sciences, Babol, I.R.Iran Mahsa Sabbaghi mdsabbaghimahsa@gmail.com 100319475328460053342 100319475328460053342 No School of Medicine, Babol University of Medical Sciences, Babol, I.R.Iran Hoda Shirafkan hodashirafkan@gmail.com 100319475328460053343 100319475328460053343 No Social Determinants of Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Seyyed Hossein Mousavie Anijdan shmosavia@gmail.com 100319475328460053344 100319475328460053344 Yes Department of Radiation Technology, Allied Medicine Faculty, Babol University of Medical Sciences, Babol, I.R.Iran