title: Effect of oral calcium loading on intact PTH and calcitriol in idiopathic renal calcium stone formers and healthy controls.
abstract: The calciuric response after an oral calcium load (1000 mg elemental calcium together with a standard breakfast) was studied in 13 healthy male controls and 21 recurrent idiopathic renal calcium stone formers, 12 with hypercalciuria (UCa x V > 7.50 mmol/24 h) and nine with normocalciuria. In controls, serum 1,25(OH)2 vitamin D3 (calcitriol) remained unchanged 6 h after oral calcium load (50.6 +/- 5.1 versus 50.9 +/- 5.0 pg/ml), whereas it tended to increase in hypercalciuric (from 53.6 +/- 3.2 to 60.6 +/- 5.4 pg/ml, P = 0.182) and fell in normocalciuric stone formers (from 45.9 +/- 2.6 to 38.1 +/- 3.3 pg/ml, P = 0.011). The total amount of urinary calcium excreted after OCL was 2.50 +/- 0.20 mmol in controls, 2.27 +/- 0.27 mmol in normocalciuric and 3.62 +/- 0.32 mmol in hypercalciuric stone formers (P = 0.005 versus controls and normocalciuric stone formers respectively); it positively correlated with serum calcitriol 6 h after calcium load (r = 0.392, P = 0.024). Maximum increase in urinary calcium excretion rate, delta Ca-Emax, was inversely related to intact PTH levels in the first 4 h after calcium load, i.e. more pronounced PTH suppression predicted a steeper increase in urinary calcium excretion rate. Twenty-four-hour urine calcium excretion rate was inversely related to the ratio of delta calcitriol/deltaPTHmax after calcium load (r = -0.653, P = 0.0001), indicating that an abnormally up-regulated synthesis of calcitriol and consecutive relative PTH suppression induce hypercalciuria.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Policlinic of Medicine, University of Berne, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Hess
authors.forename: K
authors.initials: K
authors.lastname: Lippuner
authors.forename: R
authors.initials: R
authors.lastname: Takkinen
authors.forename: L
authors.initials: L
authors.lastname: Villiger
authors.forename: D
authors.initials: D
authors.lastname: Ackermann
authors.forename: P
authors.initials: P
authors.lastname: Jaeger
mesh_terms: D000328:Adult; D002117:Calcitriol / Q000097:blood*; D002118:Calcium / Q000652:urine; D002136:Calcium, Dietary / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D016022:Case-Control Studies; D006801:Humans; D007669:Kidney Calculi / Q000209:etiology / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D013997:Time Factors
chemical_list: D002136:Calcium, Dietary; D010281:Parathyroid Hormone; D002117:Calcitriol; D002118:Calcium