Reversibility of parathyroid gland suppression in CAPD patients with low i-PTH levels.

The i-PTH response to changes in the peritoneal calcium balance was studied prospectively in a group of 13 stable CAPD patients, who presumably had adynamic bone disease, with low or normal i-PTH values and low aluminum in plasma. Five days after the reduction of dialysate calcium concentration from 1.75 mmol/l to 1 mmol/l, there was a significant elevation in the serum i-PTH. These increased PTH levels returned to baseline values when patients were changed to the 1.75 mmol/l Ca solution (p = 0.004). The changes in i-PTH mirrored the changes in peritoneal calcium balances. These results support the notion that the low or normal levels of i-PTH frequently seen in peritoneal dialysis patients are due to the hypercalcemic effects of the standard peritoneal dialysis solutions; in these patients, the parathyroid hormone production is normal since negative peritoneal balances of calcium are associated with an increase in serum i-PTH.