Measurement of vitamin D metabolites in anephric subjects.
Circulating concentrations of 1,25-dihydroxyvitamin D, 24,25-dihydroxyvitamin D and 25-hydroxyvitamin D were measured in 21 anephric subjects. 13 subjects had no therapy with vitamin D, dihydrotachysterol or 1 alpha-hydroxyvitamin D3. In 7 subjects of this group 1,25-dihydroxyvitamin D was undetectable (less than 5 pmol/l). In the other 6 patients concentrations ranged from 10 to 43 pmol/l (reference value 111 +/- 33 pmol/l). All subjects taking high doses of vitamin D showed detectable 1,25-dihydroxyvitamin D concentrations in the same range. Dihydrotachysterol therapy caused spuriously high '1,25-dihydroxyvitamin D' values, probably by interference of a metabolite of dihydrotachysterol in our assay. In subjects on vitamin D or dihydrotachysterol therapy 25-hydroxyvitamin D concentrations were significantly elevated (314 +/- 146 nmol/l and 98 +/- 19 nmol/l, respectively; reference value 52 +/- 22 nmol/l). Concentrations of 24,25-dihydroxyvitamin D were only measured in subjects without vitamin D2 intake. In general very low but detectable concentrations were found. One subject on a high dose of vitamin D3 showed a 24,25-dihydroxyvitamin D3 concentration of 10.2 nmol/l (reference value 4.4 +/- 2.9 nmol/l). Our results therefore confirm earlier reports on extrarenal synthesis of 24,25-dihydroxyvitamin D and suggest that there may be extrarenal production of 1,25-dihydroxyvitamin D as well.
D015650:24,25-Dihydroxyvitamin D 3; D015652:25-Hydroxyvitamin D 2; D002117:Calcitriol / Q000097:blood; D004097:Dihydrotachysterol / Q000627:therapeutic use; D004100:Dihydroxycholecalciferols / Q000097:blood; D004872:Ergocalciferols / Q000031:analogs & derivatives / Q000097:blood; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood*; D007668:Kidney / Q000502:physiology*; D009392:Nephrectomy; D006435:Renal Dialysis; D014807:Vitamin D / Q000627:therapeutic use
D004100:Dihydroxycholecalciferols; D004872:Ergocalciferols; D006887:Hydroxycholecalciferols; D014807:Vitamin D; D015652:25-Hydroxyvitamin D 2; D015650:24,25-Dihydroxyvitamin D 3; D002117:Calcitriol; D004097:Dihydrotachysterol