Effect of CAPD and hemodialysis on parathyroid function.

Unlabelled: A high incidence of low turnover bone disease (LTBD) has been reported in predialysis and dialysis uremic patients, despite parathyroid hormone (PTH) levels two- to four-fold the upper normal limit. The aim of this study was to evaluate the trend of PTH in uremic patients after admission to continuous ambulatory peritoneal dialysis (CAPD) or hemodialysis (HD). Thus, we evaluated 53 patients (27 CAPD and 26 HD) of 73 consecutive uremic patients starting CAPD or HD from 1992, who had at least one year follow-up on dialysis. HD and CAPD patients were comparable for age, nephropathy, and duration of uremia. All the patients had been treated with calcium carbonate (CaCO3) as the sole phosphate binder during the predialysis period. At the time of admission to dialysis PTH was > 260 pg/mL (fourfold above the upper normal limit) in 12 CAPD and 9 HD patients, between 130 and 260 pg/mL in 6 CAPD and 5 HD patients, and < 130 pg/mL in 9 CAPD and 12 HD patients. Bone biopsy, performed in 22 patients, showed LTBD in 10 of 12 patients with PTH < 130 pg/mL and high bone turnover in 8 patients with PTH > 260 pg/mL. Patients were treated with a dialysate calcium (Ca) of 1.75 mmol/L and were given CaCO3 to maintain serum phosphate < 5 mg/dL. Oral calcitriol was given if they developed hypocalcemia (< 9 mg/dL). Hypercalcemia (> 10.5 mg/dL) occurred in 13 CAPD and 17 HD patients, and was managed by discontinuation of calcitriol and reduction of dialysate Ca to 1.25-1.5 mmol/L. A significant decrease in PTH and alkaline phosphatase was observed in both groups after six and 12 months of treatment. After one year of CAPD, PTH was > 260 pg/mL in 3 patients, between 130 and 260 pg/mL in 4 (all on calcitriol), and < 130 pg/mL in 20 patients (17 on calcitriol, but only 2 mild hypercalcemic). After one year of HD, PTH was > 260 pg/mL in 3 patients, 130-260 pg/mL in 5 (all on calcitriol), and < 130 pg/mL in 18 (11 on calcitriol, 1 mild hypercalcemic).

In Conclusion: (1) about 40% of predialysis patients treated with CaCO3 showed PTH levels suggestive of LTBD; (2) the proportion of patients with low PTH increases after one year on CAPD or HD, even though calcemia was maintained within the normal range; (3) suppressed PTH levels are associated with calcitriol therapy rather than dialysis modality; and (4) secondary hyperparathyroidism improves in most patients after one year on CAPD or HD.