Comparison between the 5,6-cis and 5,6-trans isomers of 25-hydroxyvitamin D3 in chronic hypoparathyroidism.
Five patients with chronic post-operative hypoparathyroidism were treated with 450 microgram/day 5,6-trans-25-hydroxyvitamin D3 (5,6-trans-25OHD3) for 14 days, and the treatment was continued with 150 microgram/day for one year. At the end of this period the patients received 450 microgram/day 5,6-cis-25-hydroxyvitamin D3 (5,6-cis-25OHD3) for 14 days. Comparison of the effects of both isomers revealed a similar ability to enhance intestinal calcium absorption and to normalize serum calcium; serum phosphate and alkaline phosphatase, however, remained unaffected. Urinary phosphate and hydroxyproline excretion decreased on the cis-isomer and increased on the trans-isomer. During treatment with the lower dose of 5,6-trans-25OHD3 intestinal calcium absorption remained in the normal range for one year, whereas the serum calcium decreased to the levels observed before administration of 450 microgram/day within 6 weeks. The results suggest that in hypoparathyroidism 5,6-cis-25OHD3 and 5,6-trans-25OHD3 are equally effective on serum calcium and on intestinal calcium absorption, but that their mode of action on renal phosphate handling and on calcium release from bone is different.
D000328:Adult; D000368:Aged; D002118:Calcium / Q000378:metabolism; D002908:Chronic Disease; D004341:Drug Evaluation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006887:Hydroxycholecalciferols / Q000627:therapeutic use*; D007011:Hypoparathyroidism / Q000188:drug therapy*; D007408:Intestinal Absorption / Q000187:drug effects; D007536:Isomerism; D008875:Middle Aged
D006887:Hydroxycholecalciferols; D002118:Calcium