Effect of single oral phosphate loading on vitamin D metabolites in normal subjects and in X-linked hypophosphatemic rickets.
There have been several reports that document abnormal vitamin D metabolism in X-linked hypophosphatemic rickets (XLH). Those reports indicate a blunted renal 25-hydroxyvitamin D-1 alpha-hydroxylase response to a potent stimulator, phosphorus restriction. We examined here its response to phosphate supplementation. Seven normal volunteers and 12 patients with XLH were submitted to single oral phosphate loading. This treatment produced a marked elevation of the serum phosphorus level, with a mild reduction in the serum calcium level. In normal subjects, although the concentrations of intact parathyroid hormone and mid-region parathyroid hormone were increased, with two peaks at 2 and 8 h after treatment, there were no significant changes in vitamin D metabolites including 25-hydroxyvitamin D (25(OH)D), 24,25-dihydroxyvitamin D (24,25(OH)2D) and 1,25-dihydroxyvitamin D (1,25(OH)2D). On the other hand, in the patients with XLH, the serum 1,25(OH)2D level increased from 23.4 +/- 12.0 (mean +/- SD) pg/ml to 44.3 +/- 33.6 pg/ml 6 h after ingestion without any significant change in 25(OH)D or 24,25(OH)2D.
Yamaoka
K
K
Department of Pediatrics, Osaka University School of Medicine, Japan.
Tanaka
H
H
Kurose
H
H
Shima
M
M
Ozono
K
K
Nakajima
S
S
Seino
Y
Y
D015650:24,25-Dihydroxyvitamin D 3 / Q000097:blood; D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D002112:Calcifediol / Q000097:blood; D002116:Calcitonin / Q000097:blood; D002117:Calcitriol / Q000097:blood; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007015:Hypophosphatemia, Familial / Q000097:blood* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology; D012279:Rickets / Q000097:blood* / Q000378:metabolism; D014807:Vitamin D / Q000378:metabolism*
D010281:Parathyroid Hormone; D010710:Phosphates; D014807:Vitamin D; D015650:24,25-Dihydroxyvitamin D 3; D002116:Calcitonin; D002117:Calcitriol; D002112:Calcifediol