Initial [99m]Tc thyroidal kinetics in thyrotoxicosis: patterns and usefulness in differential diagnosis of toxic nodular goiter

ABSTRACT

This prospective study included 74 untreated hyperthyroid patients as well as 25 age- matched healthy controls aiming at assessment of initial Tc 99m thyroidal kinetics' patterns in different types of thyrotoxicosis, its usefulness in differential diagnosis of toxic nodular goiter, mainly discrimination between its immune and non-immune variants, compared to CDFS and to find-out which of the parameters evaluated was the best in such issue. Patients were selected and divided into four groups according to their definitive diagnosis based on clinical laboratory data, sonography and Tc 99m static thyroid scan. Group I included 23 patients with Graves ' disease, group 2 included 26 patients with toxic nodular goiter, group 3 included 10 patients with single toxic adenoma, group 4-.included 15 patients with thyroiditis. All patients,except group 4 patients, had statistically significant higher FI values compared to control subjects [p<0.05]. Moreover, group 1 and 4 patients [cases with immune thyrotoxicosis] showed statistically significant higher PI values compared to other groups [non-immune thyrotoxic patients] as well as control group [p<0.05].Group 1 and group 4 patients showed almost similar PI values [p>0.05]. Also, group 2 and 3 showed almost similar PI and FI values [p >0.05]. Retrospective analysis of PI and FI values of group 2 patients [toxic nodular goiter] revealed different behaviour of their PI values. Cases with immune variants of toxic nodular goiter had higher PI values than non-immune variants [p< 0.0001] despite their almost similar FI values and hormonal levels. Regarding the sensitivity and specificity, PI showed statistically significant higher values than those of CDFS in differentiating immune from non-immune variants of toxic nodular goiters [p<0.002 and <0.0003 respectively]. our results suggest that initial Tc 99m thyroidal kinetics done as a part of the routinely done static thyroid scan is an objective, non-invasive simple methods that can be useful in discrimination between immune and non-immune variants of toxic nodular goiter with better sensitivity and specificity than CDFS