Ectopic and Eutopic Located Parathyroid Lesions: Do They Behave Differently? How Can We Monitorize Them? What Can We Look for?

Abstract

Objective: Hyperparathyroidism (HPT) is a frequent endocrine disorder that progresses with an increase in the parathormone (PTH) synthesis and secretion from the chief cells in one or more glands. The common methods used in the imaging of parathyroid adenomas are the ultrasonography and Tc-99m sestamibi scintigraphy (MIBI) scintigraphy. We aimed to investigate the determining characteristics and availability of the MIBI scintigraphy technique in detecting eutopic and ectopic localized parathyroid adenomas. Materials and Methods: This is a retrospective study. A total of 59 patients diagnosed with primary HPT between 2002 and 2010 using parathyroid scintigraphy with Tc99m MIBI imaging and dual-phase dual-isotope technique, which was reported as parathyroid adenoma, were enrolled into this study. To determine the radiopharmaceutic retention, an early parathyroid-to-thyroid ratio (early PT/T), late parathyroid-to-thyroid ratio (late PT/T), early-to-late ratio (E/L), and the retention index (RI) were calculated. Results: The lesions were divided into two groups: ectopic (n=28) and eutopic (n=37). When biochemical parameters were compared, there was not any statistically significant difference in the physiological parameters excluding the PTH levels. We determined that the level of PTH is the only biochemical parameter that is directly associated with the positivity of MIBI. Moreover, our findings revealed that the E/L ratio is negatively correlated with Ca +2 and P, while the RI ratio exhibited a positive association with Ca +2 and P in the ectopic group. Conclusion: We concluded that the MIBI is currently the best imaging method to diagnose parathyroid adenomas. The ideal imaging protocol should include a combination of a single photon emission computerized tomography study that is not prolonged over 1 h with an early and late planar (15 min and 2 h, respectively) imaging.