Biochemical Profile of and Factors Associated With Recurrence in Primary Hyperparathyroidism.

Importance: Using biochemical profiles of patients with primary hyperparathyroidism allows surgeons to preoperatively identify patients who are more likely to have single-gland disease (SGD) vs multigland disease (MGD). Additionally, biochemical profiles may be used to monitor patients who are at increased risk for recalcitrant disease. Objective: To assess the associations of preoperative imaging localization, intraoperative parathyroid hormone (PTH) kinetics, and surgical pathology (SGD vs MGD) relative to baseline intact serum PTH, as well as establish independent risk factors for recalcitrant hyperparathyroidism. Design, Setting, and Participants: This retrospective cohort study used data from a rural tertiary care center treating adult patients who underwent elective parathyroidectomy for primary hyperparathyroidism between November 1, 2006, and January 30, 2023. Main Outcomes and Measures: Baseline serum biochemical profiles were used to stratify patients into 2 cohorts: low PTH (<100 pg/mL) and high PTH (≥100 pg/mL). Preoperative imaging results, surgical pathology results, intraoperative PTH kinetics, and long-term outcomes were compared between the 2 groups. Long-term follow-up revealed parameters of patients with biochemical recurrence. Results: Of 1202 patients in the study, 536 were included in the low-PTH cohort (mean [SD] age at diagnosis, 61.7 [12.7] years; 430 [80.2%] female) and 666 in the high-PTH cohort (mean [SD] age at diagnosis, 61.9 [13.6] years; 501 [75.2%] female), with a median (IQR) follow-up of 4.8 (8.8) years. Preoperative imaging localized more readily in the high-PTH cohort (559 patients [90.8%] vs 441 patients [83.4%]; odds ratio [OR], 1.94; 95% CI, 1.30-2.90). SGD was more likely among patients in the high-PTH group (594 [89.2%] vs 455 [84.9%]; OR, 1.47; 95% CI, 1.05-2.06). Patients with high baseline PTH tended to have more optimal intraoperative PTH kinetics than those with low baseline PTH (intraoperative PTH decline, 70.1% vs 63.6%; difference, 6.5 percentage points; 95% CI, 1.5-11.2 percentage points). Postoperatively, a calcium level of 10.0 mg/dL at 6 months was associated with recurrence (OR, 6.96; 95% CI, 3.24-14.94). Conclusions and Relevance: In this cohort study, high baseline PTH levels were associated with improved preoperative image localization and presence of SGD. Furthermore, intraoperative PTH kinetics were more optimal in patients with high baseline PTH levels. Targeted surgical approaches must be considered carefully in patients with low baseline PTH levels. Patients with postoperative calcium of 10 mg/dL at 6 months should warrant consideration of close follow-up, as these patients are more likely to have recalcitrant disease.