Minerals, vitamin D, and parathyroid hormone in continuous ambulatory peritoneal dialysis

Minerals, vitamin D, and parathyroid hormone in continuous ambulatory peritoneal dialysis. The effects of continuous ambulatory peritoneal dialysis on parathyroid hormone (PTH) and mineral metabolism were evaluated in ten patients. Utilizing a PTH radioimmunoassay, which measures both intact hormone and carboxyl-terminal PTH fragments, it was found that the mean clearance of immunoreactive parathyroid hormone was 1.5 ± 0.73ml/min (SEM) yielding a daily net removal of 13.6 ± 3.2% of estimated total extracellular parathyroid hormone. Gel electrophoresis of the dialysate revealed the presence of both intact parathyroid hormone and fragments in a similar pattern to that of peripheral plasma. Normal levels of 25-(OH) vitamin D and vitamin D binding protein were observed prior to the initiation of continuous ambulatory peritoneal dialysis and following 6 months of treatment. Timed dialysate collections (N = 93) demonstrated a daily calcium influx of only 9.9 ± 9.7mg. The daily removal of phosphorus was 308.4 ± 15.5mg. Despite elevated serum magnesium levels in all patients, the net daily removal was inadequate (31.2 ± 15.5mg). It was concluded that: (1) Unlike chronic hemodialysis, continuous ambulatory peritoneal dialysis removes significant amounts of parathyroid hormone. (2) Normal 25-(OH) vitamin D and vitamin D binding protein levels are maintained with continuous ambulatory peritoneal dialysis despite large protein losses. (3) Substantial amounts of phosphorus are removed with continuous ambulatory peritoneal dialysis but not to an extent that precludes use of phosphorus binders. (4) Dialysate containing lower magnesium and possibly higher calcium concentrations should be made available to improve mineral homeostasis. Minerals, vitamine D, et l'hormone parathyroidienne en dialyse peritoneale continue ambulatoire. Les effets de la dialyse peritoneale continue ambulatoire sur 1'hormone parathyroidienne (PTH) et le metabolisme mineral etaient evalue en 10 malades. En utilisant un dosage radio-immunologique de la PTH mesurant a la fois l'hormone intacte et les fragments carboxyl-teriminaux de la PTH, il a ete trouve que la clearance moyenne de l'hormone parathyroidienne immunoreactive etait de 1,5 ± 0,73ml/mn (SEM), ce qui donne une epuration journaliere nette de 13,6 ± 3,2% de l'hormone parathyroidienne extracellulaire totale estimee. Une electrophorese sur gel de la dialysat a montre la presence de l'hormone parathyroidienne intacte et de fragments avec un aspect similaire a celui du plasma peripherique. Des valeurs normales de 25-hydroxyvitamine D et de proteine de liaison de la vitamine D ont ete observees avant le debut de la dialyse peritoneale continue ambulatoire, et au bout de 6 mois de traitement. Des recueils repetes du dialysat (N = 93) ont demontre que 1'influx calcique journalier n'etait que de 9,9 ± 9,7mg. L'epuration journaliere de phosphore etait de 308,4 ±15,5mg. Malgre des concentrations seriques elevees de magnesium chez tous les malades, l'epuration journaliere nette de magnesium etait inappropriee (31,2 ± 15,5mg). Il etait conclu: (1) A la difference de l'hemodialyse chronique, la dialyse peritoneale continue ambulatoire retire des quantites significatives d'hormone parathyroidienne; (2) les concentrations de 25 (OH)-vitamine D et de proteine de liaison de la vitamine D se maintiennent a des valeurs normales en dialyse peritoneale continue ambulatoire, malgre d'importantes pertes proteiques; (3) des quantites substantielles de phosphate sont retirees par la dialyse peritoneale continue ambulatoire, sans toutefois que cette quantite permette l'abandon des bloqueurs de l'absorption de phosphate; (4) un dialysat contenant moins de magnesium et probablement plus de calcium devrait etre disponible afin d'ameliorer l'homeostasis minerale.