Altered calcium metabolism in chronic renal failure.

Altered calcium metabolism in chronic renal failure. A compartmental analysis of 47 Ca tracer kinetic data and Ca balance measurements was employed to evaluate several indexes of Ca metabolism in patients with mild to severe renal insufficiency. Rates of Ca accretion and resorption and the size of the exchangeable Ca pools were measured. In addition, absolute measurements were made of total body Ca, P, Cl and Na by means of neutron activation analysis. Total body K was measured by whole-body counting. Total body levels of Ca, P, Na, Cl and K in patients with modest renal insufficiency did not differ from those of a normal contrast population. In patients with severe renal failure, however, there were a number of changes in Ca and P metabolism. The total body P/Ca and P/K ratios were increased above normal. Most of the patients with renal insufficiency had total body Ca levels within the normal range, when normalized for skeletal size and the age and sex of the patient. The levels of total body Ca were inversely related to the accretion rate of Ca into bone; that is, the patients with the greatest calcium deficit had the highest accretion rate. Alterations in compartment sizes and intercompartmental transfer rates were observed in severe renal failure. The increased size of an exchangeable Ca compartment together with the essentially normal levels of total body Ca suggest a translocation of skeletal Ca to soft tissue mediated by increased parathyroid hormone secretion. Further studies, including a measure of the size of the soft tissue and skeletal compartments, are required to substantiate this hypothesis. Le modification du metabolisme du calcium dans l'insuffisance renale chronique. Une analyse compartimentale des resultats de cinetiques du traceur 47 Ca et du bilan de calcium a ete employee pour evaluer divers parametres du metabolisme du calcium chez des malades atteints d'insuffisance renale moyenne ou severe. Les debits d'accretion et de resorption et la taille des pools echangeables de calcium ont ete determines. De surcroit les mesures des masses corporelles totales de Ca, P, Cl et Na ont ete faites au moyen de l'activation neutronique. Le potassium total corporel a ete mesure par comptage corporel total. Les masses corporelles de Ca, P, Na, Cl et K des malades atteints d'insuffisance renale modest ne sont pas differentes de celles d'une population normale. Chez les malades atteints d'insuffisance renale severe, cependant, il existe des modifications des metabolismes de Ca et P. Les rapports P/Ca et P/K de l'organisme entier sont augmentes par rapport aux valeurs normales. La plupart des malades atteints d'insuffisance renale ont un Ca total dans l'eventail des valeurs normales quand les donnees sont corrigees par la masse du squelette l'âge et le sexe du malade. Le Ca total corporel est inversement correle au debit d'accretion du Ca dans l'os; c'est-a-dire que les malades qui ont le deficit en calcium le plus grand ont aussi le debit d'accretion le plus eleve. Des modifications de la taille des compartiments et des debits de transfert ont ete observes dans l'insuffisance renale severe. L'augmentation de la taille d'un compartiment de Ca echangeable alors que le Ca total corporel est normal suggere une translocation du calcium squelettique vers les tissus mous sous l'influence d'une secretion accrue d'hormone parathyroidienne. Des travaux supplementaires comprennant une mesure de la taille des compartiments tissulaires et squelettique sont necessaires pour etayer cette hypothese.