Background: Criterion requiring intraoperative parathyroid hormone (IOPTH) drops >50% from the highest, preincision or preexcision level, 10 minutes after the abnormal gland's excision predicts operative success with 98% accuracy. The purpose of this study is to correlate IOPTH dynamics with recurrent hyperparathyroidism (RecHPT) and eucalcemia with high PTH (HPTH). Methods: We followed 383 consecutive patients with parathyroidectomy guided by IOPTH monitoring using the above criterion for >6 months. Calcium and PTH levels were measured for 50 months (range, 6-173). Patients were divided in 2 groups: group 1 comprised 302 participants with IOPTH levels that decrease to the normal range (NR), and group 2, with 81 participants who had >50% IOPTH decrease but remained above the normal range. The incidence of RecHPT and eucalcemia with HPTH was evaluated. Results: RecHPT was found in 2% (8/383) of patients and eucalcemia with HPTH was present in 19% (74/383). In group 1, 17% (52/302) had eucalcemia with HPTH, whereas in group 2, this incidence was 27% (22/81; P = .04). However, only 2% of those (6/302) in group 1 and 2.5% (2/81) in group 2 developed RecHPT (P = .76). Conversely, 70.5% of those (57/81) in group 2 were eucalcemic with normal PTH. Conclusion: Although postoperative eucalcemia with HPTH was significantly higher among patients with IOPTH above the normal range than in patients in group 1, the incidence of RecHPT was not increased. The majority of patients in whom IOPTH did not drop to the normal range continue to be biochemically normal after the operation.
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