Lack of effect of 24,25-dihydroxyvitamin D3 administration on parameters of calcium metabolism.
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.
Harvey
J A
JA
Center on Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas 75235.
Zerwekh
J E
JE
Sakhaee
K
K
Pak
C Y
CY
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
D004100:Dihydroxycholecalciferols; D010281:Parathyroid Hormone; D015650:24,25-Dihydroxyvitamin D 3; D002117:Calcitriol; D002118:Calcium