Revisiting lithium-associated hyperparathyroidism in the era of intraoperative parathyroid hormone monitoring

Background. Chronic lithium therapy may cause hyperparathyroidism (HPT). The utility of intraoperative parathyroid hormone monitoring (IOPTH) in these patients is unknown. The authors' hypothesis was that multiglandular disease is more common in these patients, and the ability of IOPTH to predict cure may be limited. Methods. Twelve patients had HPT during chronic lithium therapy and underwent parathyroidectomy with IOPTH. Criteria for curative resection were a decrease ≥50% from baseline and into the normal range. Calcium and PTH levels were measured during follow-up. Results. Preoperatively, mean calcium was 11.0 ± 0.1 mg/dL, and PTH was 116 ± 14 pg/mL. Fifty percent of patients had multiglandular disease confirmed by IOPTH levels. Mean IOPTH decrease from baseline was 74 ± 4%. Although 10 of 12 patients met criteria for curative resection, only 8 remain normocalcemic. The 2 patients who did not meet criteria remain normocalcemic. Mean postoperative calcium for all patients was 9.5 ± 0.2 mg/dL. Of the 10 normocalcemic patients, 4 also have hyperparathormonemia (mean PTH, 119 ± 19 pg/mL). Conclusions. The incidence of multiglandular disease in HPT after chronic lithium exposure is higher than standard HPT. The ability of IOPTH to predict durable normocalcemia is limited. Bilateral neck exploration should be considered for these patients regardless of whether IOPTH monitoring is used.