Parathyroid Hormone-Related Protein during Pregnancy and the Perinatal Period

Abstract

To evaluate whether parathyroid hormone-related protein (PTHrP) plays any role in calcium metabolism during pregnancy and the perinatal period, we measured parathyroid hormone (PTH), immunoreactive PTHrP and calcium in maternal serum of women during pregnancy and puerperium, and in maternal and cord serum at delivery. Serum PTH levels in pregnant women were lower than those in nonpregnant women (p < 0.01). However, serum PTHrP levels were similar in the two groups of women. Cord serum total and ionic calcium levels were higher, and cord serum PTH levels were lower compared to maternal values (p < 0.01). Cord serum PTHrP levels were higher than maternal values, and umbilical arterial levels were higher than umbilical venous levels (p < 0.01). Higher levels of PTHrP in umbilical arterial blood than in umbilical venous blood suggest that the main source of cord blood PTHrP may be the fetus. PTHrP is reported to stimulate placental calcium transfer from mother to fetus in animals. The elevated cord blood PTHrP level in association with the decreased PTH level suggests that stimulation of placental calcium transfer by PTHrP may also be operative in humans.

Maternal and infant vitamin D status during the first 9 months of infant life—a cohort study

“…This is in line with the study of Bowyer et al 41 Seki et al 42 found a significantly lower PTH level in cord blood compared with maternal blood at birth, and this was in accordance with the results of Allgrove et al 43 who found low PTH levels in cord blood. They supported the contention that PTH secretion is suppressed by hypercalcemia in late fetal life, and thus Seki et al 42 suggest that stimulation of the placental calcium pump by PTHrP may be operative in humans, leading to low cord blood PTH at birth. In addition, one has to be aware that in the fetus PTH and calcium levels is probably of minor importance to circulating levels of 1,25(OH)2D, as 1,25(OH)2D levels primarily depend on the maternal supply of 25OHD.…”

Changes in serum markers of bone turnover during normal pregnancy

“…6 It has been suggested that this may be driven by parathyroid hormone (PTH); 7 however, more recent studies have shown a signi¢cant decrease in PTH during pregnancy and have suggested the possible involvement of parathyroid hormone -related protein (PTHrP). 8,9 Bone histology suggests an increase in resorption at this time, 10 and this is supported by recent studies of biochemical markers of bone turnover. 11,12 Bone mineral density measurements using dual-energy X-ray absorptiometry are di¤cult to interpret, however, with decreases at the spine but variable changes in appendicular skeleton being reported.…”

Changes in Clinical Pathology Parameters During Gestation in the New Zealand White Rabbit

“…In the present study, sodium levels fell a maximum of 6 mEq/L and potassium levels fell a maximum of 0.7 mEq/L by day 22. Chloride levels decreased 7 mEq/L and then returned to preconceptional levels on day 25. Serum calcium levels in pregnant women have been reported as continuously decreasing throughout gestation (35,53) and as progressively decreasing until some time during the third trimester (week 29) with minimal increases thereafter (48,60). Some of the decrease is a response to the fetus's requirement for calcium (60).…”