Aim: The aim of this study was to evaluate possible deterioration of salivary gland function due to radioiodine therapy with low activities using standardized quantitative salivary gland scintigraphy (qSZ). In addition, the prevalence of sialopathies was estimated in patients with thyroid dysfunction.
Methods: Prior to routine thyroid scintigraphy qSZ was performed after i.v. injection of 36-126 MBq 99mTc-pertechnetate, and both uptake and excretion fraction were calculated as a measure of parenchymal function and saliva excretion, respectively 312 healthy patients served as reference for a normal data base. 144 patients underwent qSZ prior to and 3 months after radioiodine therapy. Results of qSZ in another 674 thyroid patients were evaluated for determining the prevalence of salivary gland dysfunction.
Results: Normal uptake was 0.45 +/- 0.14% and 0.39 +/- 0.12%, and normal excretion fraction amounted to 49.5 +/- 10.6% and 39.1 +/- 9.2% in parotid and submandibular glands, respectively. Despite salivary gland stimulation with ascorbic acid during radioiodine therapy a significant activity-related functional impairment of 14-90% could be measured after application of 0.4-24 GBq of 131I. Prevalence of pretreatment sialopathies was 77/674 = 11.4% in single glands, and there was a global salivary gland functional impairment in 52/674 = 7.7%.
Conclusion: Together with thyroid scintigraphy qSZ is an easy to perform examination without additional radiation burden. It can be recommended in all patients prior to and after radioiodine therapy both in order to quantify and to document possible parenchymal impairment induced even by low activities of 131I.