Plasma Parathormone, Calcium and Phosphorus in Patients with Renal Osteodystrophy Undergoing Chronic Hemodialysis

Abstract

Plasma parathormone, calcium and phosphorus were measured during calcium infusion in patients with chronic renal failure treated by intermittent hemodialysis. Subjects with osteitis fibrosa cystica had elevated plasma concentrations of parathormone when compared with similarly dialyzed subjects without osteodystrophy (2.6±0.4 vs. 0.6±0.2 ng/ml, p<.01). In 6 of 7 patients with bone disease, plasma parathormone decreased during calcium infusion, but at comparable levels of plasma calcium it remained higher than in patients without bone disease. In vitro study of parathyroid glands from one patient with osteitis fibrosa also demonstrated responsiveness of parathormone secretion to a changing calcium environment. During the calcium infusion studies, patients with osteodystrophy had significantly smaller increments in plasma calcium than controls; this rapid uptake of iv calcium was accompanied by significant decreases in plasma phosphorus suggesting deposition in bone. Excessive but not autonomous parathormone secretion therefore appears partially responsible for renal osteitis fibrosa occurring in patients whose renal failure is otherwise ameliorated by chronic hemodialysis. In addition, it seems likely that a component of osteomalacia (deficient mineralization) accompanies the osteitis fibrosa.