Normalization of intraoperative parathyroid hormone does not predict normal postoperative parathyroid function

Background Intraoperative measurement of intact parathyroid hormone (iPTH) has been used increasingly as a means of confirming complete removal of hyperfunctioning parathyroid tissue. It remains uncertain, however, whether normalization of iPTH levels at operation accurately predicts postoperative values of iPTH. Methods Forty‐five consecutive patients with primary hyperparathyroidism underwent parathyroidectomy between March and November 1999. Baseline intraoperative iPTH levels were measured before and at manipulation, then subsequently at 5 and 10 min after tissue was removed. Follow‐up values were measured at 1‐ and 3‐month intervals. Results Before operation the mean(s.d.) iPTH concentration was 211(182) pg ml −1 with a mean serum calcium level of 11·4(1·0) mg dl −1 . In all but four patients, the final intraoperative iPTH normalized to absolute values below 60 pg ml −1 (mean 38(36) pg ml −1 ). One week after operation, serum calcium levels had returned to normal (mean 9·2(0·9) mg dl −1 ) and this correlated directly with final intraoperative iPTH values when assessed by linear regression analysis ( r = 0·373, P < 0·03). By 1 month, all but two patients were normocalcaemic (mean 9·6(0·6) mg dl −1 ) with a mean iPTH of 81(99) pg ml −1 . There was no correlation between the final intraoperative iPTH and postoperative iPTH values as determined by linear regression analysis ( r = 0·035, P < 0·881). Both patients with persistent hypercalcaemia at 1 month had appropriate intraoperative decreases in iPTH level. Conclusion Although there is significant correlation between intraoperative iPTH levels and postoperative serum calcium levels, this does not hold true for postoperative iPTH levels. There was a 4 per cent failure rate in correcting postoperative calcium levels and a 20 per cent failure rate in normalizing postoperative iPTH levels despite appropriate intraoperative decreases in iPTH. © 2000 British Journal of Surgery Society Ltd