Biochemical and pathologic factors affecting technetium-99m-methoxyisobutylisonitrile imaging results in patients with primary hyperparathyroidism

Technetium 99 m methoxyisobutylisonitrile (Tc-99m MIBI) scintigraphy represents the most commonly utilized imaging modality for the detection of the diseased gland in patients with primary hyperparathyroidism (PHPT). In this study, we aimed to identify potential biological factors with an impact on MIBI sensitivity.

A total of 147 patients with surgically confirmed parathyroid adenomas were assessed retrospectively. Data including medical history, biochemical and hormonal measurements, cervical US, Tc-99m MIBI scans as well as pathology reports were retrieved and recorded.

Of the 147 patients, there were a total of 77, 39, and 31 cases with a positive, negative, and suspicious parathyroid adenoma on Tc-99m MIBI scan, respectively. Serum calcium (Ca), parathyroid hormone (PTH) and 25 (OH) D levels were comparable among MIBI positive and negative patients [Ca: 11.5 ± 0.9 vs 11.3 ± 0.9 mg/dL (P = 0.42); PTH: 216 (146–347) vs 194 (140–317) pg/mL (P = 0.45); 25(OH)D: 8.4 (5.7–18.2) vs 10.0 (4.7–23.3) ng/mL (P = 0.64), respectively]. P-glycoprotein (P-gp) staining was negative in both groups. Also, pathological examination of tissue preparations revealed no difference in terms of the volume of the adenomas, incidence of cystic adenomas, cell-type dominance (oxyphilic cell), percent fat, and Ki-67 ratio in MIBI positive and negative groups. The rate of hyalinization was 13% in MIBI positive and 28% in MIBI negative subjects, the difference being statistically significant (P = 0.04).

Presence of hyalinization in parathyroid adenomas was found to be negatively correlated with MIBI scan results.