Interpreting Discordant Intraoperative Parathyroid Hormone Kinetics: An Operative Framework for Complex Mediastinal Parathyroid Adenomas

Ectopic parathyroid adenomas account for 6% to 16% of cases of primary hyperparathyroidism; lesions adjacent to the great vessels are among the most technically demanding to resect. Intraoperative parathyroid hormone (IOPTH) monitoring with the Miami criterion guides intraoperative cure assessment, but false-negative results arise from manipulation-induced PTH surges and inter-individual variability in clearance. We describe a 69-year-old woman with primary hyperparathyroidism due to an ectopic parathyroid adenoma superior to the pulmonary artery bifurcation, resected via median sternotomy with retroaortic dissection. Preoperative localization relied on sestamibi SPECT alone, as contrast-enhanced CT was nondiagnostic. Serial IOPTH measurements failed to satisfy the Miami criterion at any timepoint, including a marked manipulation-induced spike at 5 minutes post-excision. Postoperative biochemical normalization confirmed cure. We propose a five-step framework-confirming localization concordance, identifying causes of discordant kinetics, extending biochemical sampling, excluding multigland disease, and integrating rather than overriding monitoring criteria-for interpreting discordant IOPTH in complex mediastinal disease.