Correlation between preoperative biochemical indices and intraoperative findings in primary hyperparathyroidism

Precise preoperative imaging localization of parathyroid tumors is critical in primary hyperparathyroidism (PHPT) for choosing proper surgical methods and ensuring successful surgery, but may be challenging due to the variable size, number, and location of parathyroid tumors. This study aimed to investigate the association between biochemical indices and intraoperative parathyroid tumor size, number, location, and imaging results in a cohort of PHPT patients, and to explore whether these indices can assist in preoperative localization of PHPT.

A total of 462 patients with surgically confirmed PHPT were enrolled in this study retrospectively. Preoperative biochemical indices, including serum parathyroid hormone (PTH), plasma ionized calcium (iCa), and serum calcium (Ca), as well as the intraoperative size, number, location, and imaging results of the parathyroid tumor, were reviewed and analyzed. The correlation between preoperative biochemical indices and intraoperative parathyroid tumor size was investigated using Spearman's rank correlation. The comparison of preoperative biochemical indices between single-gland disease (SGD) and multi-gland disease (MGD), orthotopic and ectopic hyperparathyroidism, as well as imaging true positive (TP) and false negative (FN) groups, was performed using the Mann-Whitney U test.

The Spearman's rank correlation coefficient (r _s) of serum PTH, plasma iCa, and serum Ca with intraoperative parathyroid tumor maximum diameter were 0.352, 0.342, and 0.224, respectively. The r _s of serum PTH, plasma iCa, and serum Ca with intraoperative parathyroid tumor volume were 0.394, 0.355, and 0.256, respectively. Serum PTH and plasma iCa levels were weakly correlated with intraoperative parathyroid tumor size (P<0.001), while no correlation was found between serum Ca levels and intraoperative parathyroid tumor size (P<0.001). Serum PTH levels were significantly higher in ectopic hyperparathyroidism than in orthotopic hyperparathyroidism (204.8 vs. 139.7 pg/mL, P<0.001). However, plasma iCa (1.38 vs. 1.36 mmol/L, P=0.76) and serum Ca levels (2.74 vs. 2.71 mmol/L, P=0.82) were not significantly different between them. No significant differences were found in these indices between SGD and MGD (P=0.10-0.84), as well as imaging TP and FN groups (P=0.10-0.88).

Serum PTH and plasma iCa levels were weakly correlated with intraoperative parathyroid tumor size. Higher serum PTH levels tend to be associated with ectopic hyperparathyroidism. The ability of biochemical indices to reliably predict parathyroid tumor anatomical features (size, number, or location of glands) appears to be limited.