ABSTRACT

Tc-99m MIBI parathyroid scintigraphy and intact parathyroid hormone (iPTH) assay are important diagnostic tests for hyperparathyroidism. The aim of the current study was to assess the relationship between Tc-99m MIBI retention and iPTH levels in parathyroid adenoma. Thirty patients (21 female, 9 male, aged 52.47 years, range 27 to 80) who had findings on parathyroid scintigraphy compatible with parathyroid adenoma and were confirmed to have the same diagnosis after surgery were included in the study. Anterior neck imaging was performed at the 10th and 120th minutes after the intravenous administration of Tc-99m MIBI. Regions of interest were generated from the tissues of parathyroid adenoma and normal thyroid tissue, and the early (E) and late (L) parathyroid/thyroid ratios were calculated. Retention index was calculated using the formula of (LE) X100/E. The iPTH levels of the patients were between 9 to 1705 pmol/L (median: 30.5 pmol/L). The retention indexes ranged between 4 to 158 (median: 14.5). There was a significant correlation between the retention index and iPTH level (p=0.0001). As a conclusion scintigraphic visualization of parathyroid adenomas in patients with high levels of serum iPTH is better. In cases with low iPTH levels, detection of the adenoma is difficult due to decreased MIBI retention.

Keywords: Intact parathormone, parathyroid scintigraphy, Tc-99m MIBI