Perinatal parathyroid hormone, vitamin D metabolites, and calcitonin in man

Abstract

Plasma levels of calcium and of parathyroid hormone (PTH) were comparable in the mothers at delivery and in nonpregnant controls; magnesium was decreased (P < 0.001) in maternal blood; and phosphate (P < 0.001), 1,25-dihydroxyvitamin D (1,25(OH)2D) (P < 0.001), and calcitonin (CT) (P < 0.01) were raised. Cord levels of calcium (P < 0.01), magnesium (P < 0.05), and CT (P < 0.01) were higher, and PTH (P < 0.01) was lower than in the maternal blood. Levels of 25(OH)D, 1,25(OH)2D, and 24,25(OH)2D lower in fetal than in maternal blood (P < 0.01) and significant linear correlations between the vitamin D metabolites examined in mothers and neonates (P < 0.001) are consistent with a diffusion barrier across the placenta and/or different affinities of binding proteins. Plasma levels of 25(OH)D and 24,25(OH)2D were significantly related (P < 0.01), suggesting precursor product type, relationships. Levels of 1,25(OH)2D higher in arterial than in venous umbilical blood (P = 0.06, sign test; P < 0.005, paired t test) suggest that the fetus participates in the synthesis of 1,25(OH)2D. Maternal PTH was significantly related to the arteriovenous difference of 1,25(OH)2D levels (P < 0.01) in cord blood, and it possibly enhances the synthesis of 1,25(OH)2D during the final stage of fetal development.

Vitamin D3metabolites in amniotic fluid in relation with maternal and fetal sera in term pregnancies

“…The levels of amniotic fluid vitamin D 3 metabolites reported in this study, however, were of unconjugated forms, similar to those in blood serum, and were considerably higher than the levels expected, should urinary excretion be their main source. Our finding of a good correlation between 25(OH)D 3 levels of maternal and fetal cord sera and no correlation of 1,25(OH)2D 3 levels in these sera is consistent with some similar reports [2,14,27] and inconsistent with others [10,29]. We found also a good correlation between the fetal and maternal serum levels of 24,25(OH) 2 D 3 (r = 0.73; ρ < 0.01), which differs from the data of HILLMAN, et al [15] and WEISMAN et al [30].…”

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

“…Umbilical artery values are higher than those obtained from the umbilical vein (736), which suggests that it is the fetal kidneys and not the placenta that contribute much calcitriol to the fetal circulation. As in the animal models, 25-hydroxyvitamin D readily crosses the placenta (254) and achieves cord blood levels that are typically 75-100% of the maternal value at term with a fetalmaternal correlation coefficient of 0.8 -0.9 (190,264,599,713,736). Calcitriol synthesis in the fetus is likely suppressed by the high serum calcium, high phosphorus, and low PTH concentrations typically observed in cord blood.…”

“…The human data are largely consistent with the rodent data mentioned above, and differ from data obtained from fetal lambs. Calcitriol circulates at low levels in fetal blood, typically Ͻ50% of the maternal value (190,264,599,642,736). Umbilical artery values are higher than those obtained from the umbilical vein (736), which suggests that it is the fetal kidneys and not the placenta that contribute much calcitriol to the fetal circulation.…”

“…Calcitriol circulates at low levels in fetal blood, typically Ͻ50% of the maternal value (190,264,599,642,736). Umbilical artery values are higher than those obtained from the umbilical vein (736), which suggests that it is the fetal kidneys and not the placenta that contribute much calcitriol to the fetal circulation. As in the animal models, 25-hydroxyvitamin D readily crosses the placenta (254) and achieves cord blood levels that are typically 75-100% of the maternal value at term with a fetalmaternal correlation coefficient of 0.8 -0.9 (190,264,599,713,736).…”

Vitamin D and Human Pregnancy

“…This was initially thought to be mediated by 1,25(OH) 2 D, as it is known that serum levels of 1,25(OH) 2 D increase early in pregnancy and peak at twice the non-pregnant range 33,43,[48][49][50][51][52][53] . However, free concentrations of 1,25(OH) 2 D appear to increase only during the third trimester, and the peak in intestinal calcium absorption occurs well before this 54,55 .…”