Intraoperative urinary cyclic AMP monitoring in primary hyperparathyroidism

Objective: This study examined the utility of intraoperative urinary cyclic 3'5' adenosine monophosphate (UcAMP), an indicator of parathyroid (PTH) hormone end-organ activity, as a 'biochemical frozen section,' signaling the real-time resolution of PTH hyperactivity during surgery for primary hyperparathyroidism. Summary Background Data: The unsuccessful initial neck exploration for primary hyperparathyroidism, leaving the patient with persistent hyperfunctioning parathyroid tissue, results in part from the surgeon's inability intraoperatively to correlate a gland's gross appearance and size estimation with physiologic function. Preoperative imaging, intraoperative imaging, and intraoperative histologic/cytologic surveillance have not resolved this dilemma. Methods: Twenty-seven patients underwent a prospective intraoperative UcAMP monitoring protocol. The patients all had a clinical diagnosis of primary hyperparathyroidism and an average preoperative serum calcium of 12.0 ± 0.3 mg/dl. UcAMP was assayed intraoperatively using 20-minute nonequilibrium radioimmunoassay providing real-time feedback to the operating team. Results: All patients had an elevated UcAMP confirming PTh hyperactivity at the beginning of the procedure. One patient, subsequently found to have an supernumerary ectopic adenoma, had four normal glands identified intraoperatively, and his intraoperative UcAMP values corroborated persistent hyperparathyroidism, the UcAMP of the remaining 26 patients decreased from 7.0 ± 1.1 to 2.7 ± 0.7 nm.dl GF (p <.00005) after complete adenoma excision, and they remain normocalcemic. The protocol provided useful and relevant information to the operating team, and aided in surgical decision-making, in 10 of the 27 cases (37%). Conclusion: Intraoperative biochemical surveillance with ucAMP monitoring reliably signals resolution of PTH hyperfunction. It is a useful adjunct to the surgeon's skill, judgment, and experience in parathyroid surgery.