Levels of 24,25-Dihydroxyvitamin D₃, 25-Hydroxyvitamin D₃ and 25-Hydroxyvitamin D₃ 3-Sulphate in Human Plasma

Abstract

The concentrations of (24R)-24,25-dihydroxyvitamin D3[24,25(OH)2D3], 25-hydroxyvitamin D3[25(OH)D3] and its 3-sulphate [25(OH)D3(3)S] in the plasma of healthy subjects, patients with chronic renal failure, patients with climacteric syndrome, pregnant women and foetuses were determined using the enzyme-linked immunosorbent assay and high-performance liquid chromatography. 25(OH)D3(3)S was not detected in about one-third of the plasma samples from patients with chronic renal failure (n = 26). The three metabolites in maternal plasma reached the highest levels in the second trimester of pregnancy followed by a decrease to the values obtained in the first trimester. Older healthy women (age range 44-71 years) showed higher levels of 24,25(OH)2D3 and 25(OH)D3 in the plasma than did young healthy women (age range 21-29 years), whereas no clear difference was observed between the older healthy women and patients with climacteric syndrome. The level of 25(OH)D3(3)S in the plasma was higher in the latter patients than in healthy women.

Determination of 24,25‐dihydroxyvitamin D3 in human plasma using liquid chromatography‐mass spectrometry after derivatization with a Cookson‐type reagent

“…The plasma level of 24,25(OH) 2 D 3 was 0.91 AE 0.42 ng/mL, which was compatible with results previously reported (Masuda et al, 1997;Higashi et al, 1999b).…”

Upregulation of calcitriol during pregnancy and skeletal recovery after lactation do not require parathyroid hormone

“…Investigators concluded from these data that trophoblast synthesis of calcitriol is “unfettered” by degradation to 24‐hydroxylated forms because Cyp24a1 may be comparatively silenced by methylation . However, numerous functional studies have shown that human and rodent placentas preferentially metabolize 25(OH)D to 24,25‐dihydroxyvitamin D and not to calcitriol; consequently, serum levels of 24‐hydroxylated forms are up to 40‐fold higher than calcitriol in human, rodent, and sheep fetuses . Our comparison of placentas to maternal kidneys, rather than decidua, may give a better indication as to the relative contribution of the placenta to synthesis and catabolism of calcitriol.…”

Bone Development and Mineral Homeostasis in the Fetus and Neonate: Roles of the Calciotropic and Phosphotropic Hormones

“…These findings have prompted other researchers to conclude that trophoblast synthesis of calcitriol is unopposed or "unfettered" by catabolism into 24-hydroxylated forms (383,479). However, the available functional data suggest the opposite conclusion, that human placentas preferentially metabolize 25-hydroxyvitamin D to 24,25-dihydroxyvitamin D instead of calcitriol (572), resulting in up to 40-fold higher concentrations of 24-hydroxylated forms compared with calcitriol in cord blood (152,253). These findings are the same as in fetal rodents, as noted above.…”