title: Lack of effect of 24,25-dihydroxyvitamin D3 administration on parameters of calcium metabolism.
abstract: Seven patients with disordered calcium metabolism and high normal or elevated serum 1,25-dihydroxyvitamin D [1,25-(OH)2D] were studied before and after the administration of 24,25-(OH)2D3 to determine its effects on calcium metabolism. Despite a significant increase in the mean serum 24,25-(OH)2D level [2.1 +/- 0.6 (+/- SE) to 16.7 +/- 6.2 nmol/L; P less than 0.05] after a daily dose of 20 micrograms for 1 month, there were no consistent changes in serum calcium, immunoreactive PTH, or 1,25-(OH)2D concentrations. Intestinal calcium absorption and urinary calcium excretion rose slightly during 24,25-(OH)2D administration in the majority of the patients. In the three patients in whom it was measured, serum 1,24,25-trihydroxyvitamin D levels did not change (19 +/- 5 vs. 20 +/- 5 pmol/L). We conclude that exogenous 24,25-(OH)2D3 at this dose has no significant antagonistic action on 1,25-(OH)2D and may have weak agonistic action.
authors: Center on Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas 75235.
authors: J A
authors: JA
authors: Harvey
authors: J E
authors: JE
authors: Zerwekh
authors: K
authors: K
authors: Sakhaee
authors: C Y
authors: CY
authors: Pak
mesh_terms: D015650:24,25-Dihydroxyvitamin D 3; D000328:Adult; D002117:Calcitriol / Q000097:blood*; D002118:Calcium / Q000378:metabolism; D004100:Dihydroxycholecalciferols / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D006934:Hypercalcemia / Q000097:blood*; D006961:Hyperparathyroidism / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood
chemical_list: D004100:Dihydroxycholecalciferols; D010281:Parathyroid Hormone; D015650:24,25-Dihydroxyvitamin D 3; D002117:Calcitriol; D002118:Calcium