Estimated weight of the residual parathyroid gland after parathyroidectomy using plasma levels of the parathyroid hormone

The possibility of estimating the total weight of the parathyroid glands based on the plasma concentration of the parathyroid hormone (PTH) would be of great help when searching for the parathyroid glands during surgery on patients with secondary hyperparathyroidism. Thus, we studied the relationship between the levels of carboxylterminal PTH (C-PTH), midportion PTH (M-PTH) and intact PTH, and the weight of the parathyroid glands resected for secondary hyperparathyroidism. The subjects studied were 11 patients with secondary hyperparathyroidism caused by chronic renal failure. The pre- and post-operative differences in the plasma C-PTH levels and plasma M-PTH levels were significantly correlated with the weight of the resected parathyroid glands (p<0.001 for both), but there was no correlation between the differences in the levels of intact PTH and the weight of the resected parathyroid glands. From these relationships we estimated the weight of the residual parathyroid gland after parathyroidectomy using the levels of each PTH. All patients in whom the residual parathyroid gland was estimated to be heavy based on the levels of M-PTH showed recurrence of hyperparathyroidism after the parathyroidectomy. We therefore found that estimation of the weight of the parathyroid glands from the levels of M-PTH is both possible and useful.