THE EFFECT OF DIALYSATE CALCIUM CONCENTRATION AND l α‐HYDROXY VITAMIN D, ON SKELETAL CALCIUM LOSS AND HYPERPARATHYROIDISM IN H AEMO DIA L YSIS PATIENTS

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Abstract
SUMMARY: The response of hyperparathyroidism and skeletal calcium loss in haemodialysis patients to treatment with lα‐hydroxyvitamin D3 and a dialysate calcium concentration of 1.375 mmol/l was compared with the response to treatment with a dialysate calcium concentration of 1.375 or 1.75 mmol/l alone over a 6 month period.In patients treated with l α‐hydroxyvitamin D3 there was a significant rise in plasma calcium associated with a significant fall in plasma alkaline phosphatase and plasma parathyroid hormone as well as resolution of sub‐periosteal erosions. In these patients there was a significant rise in the calcium content of the forearm assessed by neutron activation analysis in comparison to patients treated with a dialysate calcium concentration of 1.75 or 1.375 mmol/l alone.In patients treated with a dialysate calcium concentration of 1.375 or 1.75 mmol/l alone there was no significant change in the plasma calcium, alkaline phosphatase or parathyroid hormone after 6 months and in these patients subperiosteal erosions either did not change or became worse. No significant difference in the response in these two groups was observed.This study indicates that treatment of haemodialysis patients with 1α‐hydroxyvitamin D3 is significantly more effective than treatment with a dialysate calcium concentration of 1.375 or 1.75 mmol/l alone in preventing progression of hyperparathyroidism and skeletal calcium loss.The concentration of calcium in the dialysis fluid influences both parathyroid hormone (FTH) secretion and bone mineral loss in haemodialysis patients (Bone et al., 1972; Goldsmith & Johnson, 1973; Bouillon et al., 1975). On the basis of such evidence it has been suggested that use of a high dialysate calcium may delay progression of renal osteodystrophy (Coldsmith & Johnson, 1973). However, this is not successful in all patients (Regan et al., 1976).The recent availability of synthetic active metabolites of vitamin D3 has renewed interest in the treatment of renal osteodystrophy. In most haemodialysis patients treated with 1α‐hydroxyvitamin D3 (1α‐OHD3) there has been improvement in hyperparathyroidism and bone mineralisation (Junior et al., 1976; Pierides et al., 1976) as well as a rise in skeletal calcium content (Catto et al., 1975; Naik et al., 1976). However, in some patients treatment with 1α‐OHD3, has been associated with either no change, or deterioration in renal osteodystroph (Naik et al., 1976; Pierides et al., 1976;Winney et al., 1977).The present study compares the response of hyperparathyroidism and skeletal calcium loss to’treatment with lα‐OHD3 and a dialysate calcium concentration of 1.375 mmol/l with the response to treatment with a dialysate calcium concentration of 1.375 or 1.75 mmol/l alone. In patients treated with lα‐OHD3, the dialysate calcium concentration was reduced to 1.375mmol/I since in a previous study (Winney et al., 1977), use of lα‐OHD3 in patients treated with a dialysate calcium concentration of 1.75 mmol/l and a normal dietary calcium was associated with hypercalcaemia.
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