EFFECTS OF SUBCUTANEOUS CALCITRIOL ADMINISTRATION ON PLASMA CALCIUM AND PARATHYROID-HORMONE CONCENTRATIONS IN CONTINUOUS AMBULATORY PERITONEAL-DIALYSIS UREMIC PATIENTS

Objective: To ascertain whether the parathyroid hormone (PTH) secretio n of continuous ambulatory peritoneal dialysis (CAPD) uremic patients could be suppressed by repeated subcutaneous injections of calcitriol (CLT). Design: Nonrandomized prospective study with weekly evaluation. Setting: Hospital CAPD clinic. Patients: Seven uremic CAPD patients w ith signs of severe hyperparathyroidism.Interventions: Patients were t reated with CLT (2 mug), injected subcutaneously three times a week, o n alternate days over a period of 8 weeks. Measurements: Plasma PTH, i onized calcium (Ca), serum phosphate (Pi), and alkaline phosphatase (A P) were assayed before the start of CLT therapy and weekly thereafter. Results: The average basal PTH was 349+/-26 pg/mL (mean+/-SD). It fel l significantly by the fifth week to 158+/-20, then leveled off. Analy sis of the individual data, however, revealed that only 5 of 7 patient s had a significant decrease in plasma PTH. Basal Ca was +/-.02 mmol/L ; it increased continuously throughout the study, significantly by the fourth week, reaching a level of 1.33+/-0.3 mmol/L at the sixth week, then declined slightly. In those patients with significantly decrease d PTH, there was an inverse correlation between PTH and the correspond ing Ca levels. Conclusions: In some CAPD patients subcutaneous adminis tration of CLT significantly suppresses PTH. This effect is mainly med iated via an increase in ionized calcium, but a direct inhibitory effe ct of the vitamin on parathyroid glands cannot be excluded.