Endocrine Abstracts

Tc- 99m Sestamibi parathyroid scan (SP scan) is performed to identify location of either hyperplastic or adenomatous gland(s) in primary hyperparathyroidism (HPT). In this study we evaluated diagnostic outcome in 55 consecutive patients with clinical diagnosis of HPT who were referred for SP scans and subsequently had parathyroid surgery. These patients with HPT were of 66.9+12.46 (mean + SD) age, and had serum calcium 10.9+0.93 mg/dl, phosphorus 3.0+0.51 mg/dl, chloride 107+3 mEq/L, chloride/phosphate ratio 36.9+5.4, creatinine 1.16+0.32 mg/dl, and intact parathyroid hormone level 132+83 pg/ml. SP scans were performed early (at 0 to 30 min) or delayed (90 to 210 min) following injection of 20 mCi of Tc- 99m Sestamibi. Of 55 patients, SP scan finding were concordant with surgical findings in 36 (66%) patients. In 19 patients (34%) SP scan findings were discordant with surgical finding. All 19 discordant scans were reevaluated. Of 19 discordant SP scans, four were read as adenoma. An adenoma and one large hyperplastic parathyroid gland were found in one of these four, and in the other three the adenoma was actually found contralateral to the side indicated on the scan. The scan findings were confirmed at reevaluation. In the reevaluation of remaining 15 discordant SP scans read as hyperplasia, the previous SP scans reading was confirmed in three patients. However, in 12 patients a focally increased radioisotopic uptake was present during the early images of SP scan but not in the delayed images. The early increased focal radioisotopic uptake in these SP scans coincided with surgical findings of parathyroid adenomas in all 12 patients thus increasing SP scan concordance to surgical outcomes to 87% (48 of 55 SP scans). These findings suggest that in HPT careful evaluation of early increased radioisotopic uptake during SP scan can be important in identifying parathyroid adenomas when delayed images show no focal retention of radiotracer.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.