The relationship between semiquantitative parameters derived from technetium-99m metoxyisobutylisonitrile dual-phase parathyroid single-photon emission computed tomography images and disease severity in primary hyperparathyroidism.

Objective: The relationship between multiple semiquantitative indices on technetium-99m metoxyisobutylisonitrile (Tc-99m MIBI) parathyroid single-photon emission computed tomography (SPECT) and clinical, laboratory, and radiological data was investigated in primary hyperparathyroidism.

Patients And Methods: Ninety-three patients who had a histopathologically confirmed single parathyroid adenoma (PT) were enrolled. Regions of interests were drawn around the PT, neighboring thyroid (T), and background in early and late planar images and isocontour regions of interests around the adenoma in SPECT images (PT SPECT). The relationships between early and late PT, parathyroid adenoma counts/neighboring thyroid counts, parathyroid counts-thyroid counts (PT-T), PT washout, retention index, PT SPECT and serum parathormone (PTH), Ca, P, urinary Ca levels, weight of the adenoma, neck ultrasonography, renal ultrasonography, and bone mineral density findings were investigated.

Results: There was a positive correlation between the weight of the adenoma and serum PTH and calcium (Ca) levels (P<0.001), between serum PTH and Ca levels (P<0.001), early PT-T and serum Ca levels (P=0.027), late PT-T and weight of the adenoma (P=0.04), and PT SPECT and serum Ca levels (P=0.046) and a reverse correlation between PT SPECT and serum phosphorus (P) levels (P=0.04). Serum Ca levels were significantly higher and P levels were lower in the group with PT SPECT values above 116. PT SPECT and late parathyroid adenoma counts/neighboring thyroid counts values were significantly higher in the group with serum Ca levels of more than 11 mg/dl. Femoral T and Z scores were significantly lower in patients with lower PT washout. Early PT was significantly lower in patients with coexisting thyroiditis compared with patients with both thyroiditis and thyroid nodules (P=0.034).

Conclusion: Semiquantitative evaluation of a Tc-99m MIBI parathyroid SPECT study may help predict disease severity in primary hyperparathyroidism.