Intraoperative decay profile of intact (1–84) parathyroid hormone in surgery for secondary hyperparathyroidism in a consecutive series of 50 patients on haemodialysis

Abstract

Abstract Background The usefulness of rapid intraoperative monitoring of intact (1–84) parathyroid hormone (PTH) is not clearly defined in the surgical management of secondary HPT in the patients on haemodialysis. The aim of this study was to define the normal pattern of decay during surgery for secondary HPT using the rapid intact (1–84) PTH assay during operation. Methods Fifty patients on haemodialysis underwent neck exploration for secondary HPT. The therapeutic goal in all patients was the subtotal resection of four or more glands and bilateral transcervical thymectomy. PTH levels were monitored using a rapid immunochemiluminometric assay. Peripheral blood samples were assayed at induction of anaesthesia, after dissection but before resection, and 20 and 40 min after resection in all patients. All patients were followed up for at least 6 months. PTH levels were expressed as absolute values, as multiples of the upper limit of normal and as the percentage decline from pre-excision values. Results Forty-eight patients (96 per cent) were considered cured after surgery. Twenty patients (40 per cent) had a PTH level less than twice normal and 20 patients (40 per cent) had a PTH level between two and four times normal at 20 min. At late follow-up, all these patients were cured. Ten patients (20 per cent) had a PTH level greater than four times normal at 20 min. Eight of these patients were cured. Seven of these eight had a PTH level at 20 min, while not less than four times normal, less than 40 per cent of the original value. In contrast, the two failures had neither a decline to less than four times normal nor a decay to less than 40 per cent of the original value. One has been reoperated with resection of a fifth gland and one awaits reoperation. Conclusion The intraoperative decay of PTH during surgery for secondary HPT in patients on haemodialysis is slower than that in patients with normal renal function. However, 20 min after resection, a decline to less than four times the upper limit of normal is predictive of cure. Variability of decay slopes in individual patients may reflect molecular heterogeneity or biphasic metabolism of the hormone.