Objectives: Tertiary hyperparathyroidism, characterized by autonomous overproduction of parathyroid hormone, can be seen in patients with long-standing secondary hyperparathyroidism (pretransplant) or after renal transplant (posttransplant). Parathyroid scintigraphy and ultrasonography are the most commonly used imaging procedures for the preoperative localization of abnormal parathyroid glands. We aimed to evaluate imaging findings in pretransplant and posttransplant tertiary hyperparathyroidism.
Materials and methods: This study included 32 patients with pretransplant tertiary hyperparathyroidism and 20 patients with posttransplant tertiary hyperparathyroidism. On parathyroid scintigraphy with technetium-99m sestamibi, early-phase and latephase images were acquired. Images were evaluated for the presence and the number of active foci and the degree of uptake on the late-phase image. The existence of an autonomous gland was based on latephase retention and was scored from 0 to 2 (retention score). On ultrasonography, the criteria threshold for autonomy was the maximum length of the largest gland ≥10 mm (ultrasonography score).
Results: On parathyroid scintigraphy, the most commonly observed pattern in the pretransplant group was positivity in ≥3 glands, and in the posttransplant group the most commonly observed pattern was positivity in 1 to 2 glands. In pretransplant and posttransplant groups, the criteria threshold for the presence of an autonomous parathyroid gland on parathyroid scintigraphy (grade 2 retention) was met in 26 (81%) and 9 (45%) patients and on ultrasonography in 25 (78%) and 10 (50%) patients, respectively. In the whole group of patients (n = 52), correlation existed between ultrasonography score and retention score. Glandular weight was correlated with both retention score and ultrasonography score.
Conclusions: Higher numbers of detectable glands and the presence of parathyroid autonomy were more common in the pretransplant group. This might be explained by parathyroid gland involution after transplant. The results may also suggest that factors other than autonomy are responsible for posttransplant tertiary hyperparathyroidism.