High prevalence of abnormal uptake in thyroid gland on salivary gland scintigraphy of subjects with xerostomia symptom

Objectives Althogh Sjögren’s syndrome (SS) is the second most frequent cause of xerostomia, autoimmune thyroid diseases also involve salivary glands. The aim of our study was to estimate the prevalence of thyroid diseases (TD) in subjects with a symptom of xerostomia and to evaluate salivary gland scintigraphy (SGS) as a method to detect the TD in the patients with or without SS.

Methods Retrospectively reviewed SGS in 173 (M:F = 29:144) subjects with a symptom of xerostomia. About 20 min after the administration of 370 MBq Tc-99m pertechnetate, static images were obtained before and after sialogogue stimulation. Ejection rates were calculated for the parotid and the submandibular glands. Thyroid gland was included in the field of view. Visual assessment of the tracer uptake in the thyroid gland on the SGS and serologic thyroid function tests were used to diagnose TD.

Results Based on American_European Criteria, 36 patients (20.8%) had primary SS and 58 patients (33.5%) had secondary SS; 38 patients was changed secondary SS from primary due to TD. On visual assessment, 53 patients (30.6%) had diffusely increased and 29 patients (16.8%) had diffusely decreased tracer uptake in the thyroid gland on SGS. Although TD was observed in 49.5% of subjects with normal uptake pattern of salivary gland (n = 45/91), 41 patients had TD without SS. Abnormal uptake pattern of thyroid gland on the SGS was significantly related with TD (AUC:0.886, sensitivity 96.2%, specificity:83.2%, p<0.0001).

Conclusions More than half of patients with xerostomia had TD and the TD can be easily assessed tracer uptake in thyroid gland on the SGS. SGS might be first imaging study for assessing TD in patients with symptom of xerostomia. Therefore, in case of interpretation of the SGS, tracer uptake in the thyroid gland should not be overlooked.