Surgical Management of Normocalcemic Primary Hyperparathyroidism and the Impact of Intraoperative Parathyroid Hormone Testing on Outcome

Objective: To review our surgical experience and the impact of intraoperative parathyroid hormone (IOPTH) testing among patients with normocalcemic primary hyperparathyroidism. Study Design: Case series with chart review. Setting: Academic referral hospital. Subject and Methods: Normocalcemic hyperparathyroidism (NCHPT) patients were identified with normal-range blood ionized calcium and serum elevated parathyroid hormone. Patient demographics, intraoperative findings, IOPTH dynamics, and biochemical outcomes were compared with those of classic primary hyperparathyroidism (PHPT) patients. Results: Of the 2120 patients who underwent parathyroidectomy, 616 patients met the inclusion criteria: 119 (19.5%) patients had NCHPT, and 497 (80.5%) had classic PHPT. NCHPT patients had higher rates of multigland hyperplasia as compared with classic PHPT (12% vs 4%, P =.002) and smaller gland size (P <.001). Of 119 NCHPT patients, 114 (97%) achieved >50% drop in IOPTH intraoperatively, as opposed to 492 (99%) among 497 classic PHPT patients (P =.014). IOPTH drop >50% had an equivalent positive predictive value for long-term cure in both groups. Conclusions: Surgeons treating NCHPT patients should suspect the presence of multigland disease and have a low threshold for converting to bilateral exploration depending on IOPTH decay dynamics.