Can we use 99mTc-MIBI in functional studies of the parathyroid gland?

Abstract

The usefulness of technetium-99m-sestamibi (99mTc-MIBI) in patients with secondary hyperparathyroidism on haemodialysis was assessed. We studied 33 patients with parathyroid scintigraphy with i.v. (99mTc-MIBI). Static images in a scintillation camera were taken at 15 and 120 min after the injection. With P x Ca<80, we performed an inhibition test with calcitriol i.v. 2 microg, three times a week, for 2 weeks. The MIBI study and assessment of intact parathyroid hormone (iPTH) were performed before (baseline study) and after inhibition. A 'focal positive study' corresponded to one or more areas of abnormal hypercaptation in relation to surrounding thyroid tissue seen in early images and persisting in later images, and a 'negative study' did not correspond to the previous image. In the baseline study, iPTH in the positive MIBI group was significantly greater than in the negative group. Eight positive MIBI patients had a bone biopsy; six corresponded to severe osteitis fibrosa and two to mild osteitis fibrosa. In the negative MIBI group, four of the six patients who had bone biopsy had mild forms of osteitis fibrosa (Fisher=0.03); the other two had low turnover forms. A positive inhibition test was defined when the basal uptake disappeared after calcitriol administration. In these patients, we observed a significant decrease of iPTH, not observed in the negative inhibition test. In 10 patients who had been parathyroidectomized, those with alpha positive basal MIBI result had a nodular parathyroid hyperplasia. We conclude that a scintigraphic parathyroid study with 99mTc-MIBI showed a good correlation with functional parathyroid status. With the same inhibition test, only some glands were inhibited, suggesting that this could be the expression of different vitamin D receptor densities in inhibited glands and/or a different kind of proliferation in those glands. This test would be of value in functional studies when a therapeutic decision must be made.

MIBI scintigraphy, indicators of cell proliferation and histology of parathyroid glands in uraemic patients

“…In fact, Piga et al [11] stated that MIBI scans do not simply reveal parathyroid enlargement but rather identify hyperfunctioning parathyroid glands in patients with SHP. Indeed, Ambrosoni et al [12] confirmed this finding, affirming that in those patients who were to have total PTx, MIBI scans can facilitate the selection of the best parathyroid tissue to use for autografting [4]. Additional evidence that MIBI shows the functional status of parathyroids is found in the correlation between MIBI and intact PTH in SHP, recently demonstrated by Hung et al [13].…”

Comparison of Histological Findings and Parathyroid Scintigraphy in Hemodialysis Patients with Secondary Hyperparathyroid Glands

“…Tc-MIBI is sequestered inside the cytoplasm and mitochondria, and its degree of cellular incorporation and retention depends on the electric potential generated through the cellular and mitochondrial membrane [31]. However, the actual mechanism of radiotracer captation in the hyperplastic parathyroid tissue has yet to be completely understood [32]. Nevertheless, we demonstrated for the first time the positive association between Tc-MIBI and Tetro scintigraphy and subtypes of hyperplasia.…”

Preoperative evaluation of hyperparathyroidism: the role of dual-phase parathyroid scintigraphy and ultrasound imaging

“…Some investigators have shown a correlation between serum iPTH levels and MIBI uptake in primary and secondary hyperparathyroidism [27,[30][31][32]. Others could not fi nd such a relationship [24].…”