Lack of influence of recombinant human erythropoietin on parathyroid function in hemodialysis patients with secondary hyperparathyroidism.

The effects of recombinant human erythropoietin (rHuEPO) treatment on parathyroid function in patients on maintenance hemodialysis (HD) with secondary hyperparathyroidism (HPT) is poorly understood. We compared the levels of serum intact parathyroid hormone (PTH) and the suppressibility of PTH by intravenous calcium infusion before and after 12 weeks of rHuEPO treatment in 8 HD patients with secondary HPT. The suppressibility of PTH by calcium infusion in HD patients was also compared with that of normal subjects. After rHuEPO treatment, in HD patients hematocrit and hemoglobin levels increased significantly from 20.1 +/- 1.3% and 6.65 +/- 0.46 g/dl to 28.7 +/- 1.0% and 9.68 +/- 0.39 g/dl, respectively. The serum intact PTH levels did not change significantly (541.9 +/- 65.3 pg/ml before versus 572.9 +/- 75.3 pg/ml after rHuEPO treatment), nor did serum ionized calcium, phosphate, magnesium, aluminum, alkaline phosphatase, and 1.25(OH)2D levels. Calcium infusion significantly increased serum ionized calcium and suppressed serum PTH levels. However, the increment in serum calcium levels and the percent decrement of serum PTH showed no significant differences before and after rHuEPO treatment in HD patients. Elevations in serum calcium levels during calcium infusions were not significantly different between normal subjects and HD patients. However, the percent maximal decrement in serum PTH level was less in HD patients both before and after rHuEPO treatment than in normal subjects (-75.4 +/- 3.9 and -76.4 +/- 4.1% versus -91.4 +/- 1.4%). We conclude that rHuEPO treatment has no influence on parathyroid function in maintenance HD patients with secondary HPT. In addition, PTH secretion is less suppressed by calcium infusion in the same group of patients.