Assessment of acute parathyroid responsiveness to high calcium dialysate in uremic patients.

The response of the parathyroid glands to dialysis-induced changes in calcium has been studied in 83 normocalcemic patients receiving maintenance hemodialysis. Predialysis concentrations of intact parathyroid hormone (iPTH) were normal in 13 patients; 70 patients had increased iPTH levels of different degrees. All patients had analytically significant changes in total serum calcium (2.3 +/- 0.2 vs 2.8 +/- 0.2 mmol/l) without additional parenteral calcium loading during a standard dialysis session with a dialysis solution of 1.75 mmol calcium chloride. During hemodialysis the concentration of iPTH fell in 77 patients and was normalized in 48 of these patients. The remaining 6 patients showed no or an inadequate response (less than 30% suppression of predialysis iPTH) to the increase in Ca. Parathyroidectomy was performed in patients with refractory iPTH secretion. Histological evidence of marked parathyroid hyperplasia was obtained in all these patients. All patients with normal or partial responsiveness of the parathyroids tolerated at least small doses of 1.25 (OH)2-vitamin D3. Quantification of predialysis and postdialysis iPTH concentrations is a useful and simple method for identifying those uremic patients with true autonomy of the parathyroid glands at an early stage.