title: Effect of chronic intravenous calcitriol on parathyroid function and set point of calcium in dialysis patients with refractory secondary hyperparathyroidism.
abstract: This study evaluates the effect of intravenous calcitriol on parathyroid function and ionized calcium-PTH sigmoidal curve obtained during low- and high-calcium haemodialysis in 10 patients with osteitis fibrosa whose secondary hyperparathyroidism was refractory to conventional therapy. After 4 months of intravenous calcitriol, serum ionized calcium increased from 1.28 +/- 0.08 to 1.37 +/- 0.11 mmol/l (P less than 0.001), serum phosphate from 1.54 +/- 0.18 to 1.79 +/- 0.4 mmol/l (P NS), serum calcitriol from 16.7 +/- 9.9 to 34.3 +/- 6.4 pg/ml (P less than 0.001), while alkaline phosphatase decreased from 366 +/- 340 to 226 +/- 180 IU/l (P less than 0.05), osteocalcin from 46.4 +/- 20 to 34.5 +/- 15.3 ng/ml (P less than 0.05), and basal intact PTH from 1069 +/- 700 to 305 +/- 270 (P less than 0.01). Basal PTH started to decrease after 1 month of treatment prior to the increase in the ionized calcium. Because of hypercalcaemia the dialysate calcium was decreased from 1.75 to 1.5 mmol/l in three of five patients on haemodialysis, and calcium-containing solutions were replaced by calcium-free fluids in four of five patients on haemodiafiltration. Calcitriol dose, at the first month of therapy was 5.6 +/- 0.8 micrograms/week, but it was successively decreased because of hypercalcaemia to a final dose of 3.6 +/- 1.3 micrograms/week. After intravenous calcitriol the ionized calcium-PTH sigmoidal curve shifted to the left and downward. Maximally stimulated PTH and maximally inhibited PTH obtained during low- and high-calcium dialysis significantly decreased, as well as the ratio of basal PTH/PTHmax and the set point of calcium.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Servizio Dialisi, Ospedale Maggiore, Lodi, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Malberti
authors.forename: M
authors.initials: M
authors.lastname: Surian
authors.forename: P
authors.initials: P
authors.lastname: Cosci
mesh_terms: D002117:Calcitriol / Q000008:administration & dosage / Q000627:therapeutic use*; D002118:Calcium / Q000097:blood*; D006801:Humans; D006934:Hypercalcemia / Q000209:etiology; D006962:Hyperparathyroidism, Secondary / Q000097:blood / Q000188:drug therapy*; D007275:Injections, Intravenous; D010281:Parathyroid Hormone / Q000097:blood*; D006435:Renal Dialysis
chemical_list: D010281:Parathyroid Hormone; D002117:Calcitriol; D002118:Calcium