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Parathyroid hormone-related protein during pregnancy and the perinatal period
1Department of Obstetrics and Gynecology, National Defense Medical College, Saitama, Japan.
Insights
Parathyroid hormone-related protein (PTHrP) may aid human fetal calcium transfer during pregnancy. Lower maternal PTH and higher fetal PTHrP suggest PTHrP stimulates placental calcium transport.
Area of Science:
- Endocrinology
- Reproductive Biology
- Mineral Metabolism
Background:
- Calcium homeostasis is critical during pregnancy.
- Parathyroid hormone (PTH) and parathyroid hormone-related protein (PTHrP) are key regulators of calcium.
- The role of PTHrP in human pregnancy calcium metabolism is not fully understood.
Purpose of the Study:
- To investigate the role of PTHrP in maternal and fetal calcium metabolism during pregnancy and the perinatal period.
- To compare PTH and PTHrP levels in maternal and cord serum.
- To assess the potential involvement of PTHrP in placental calcium transfer.
Main Methods:
- Measured serum parathyroid hormone (PTH) and immunoreactive PTHrP levels.
- Analyzed maternal serum during pregnancy and puerperium.
- Collected and analyzed maternal and cord serum at delivery.
Main Results:
- Maternal PTH levels were lower in pregnant women compared to nonpregnant women.
- Cord serum total and ionic calcium levels were higher than maternal levels.
- Cord serum PTHrP levels were elevated compared to maternal levels, with higher concentrations in umbilical arterial than venous blood.
Conclusions:
- Fetal production is likely the primary source of cord blood PTHrP.
- Elevated fetal PTHrP, coupled with decreased maternal PTH, suggests PTHrP stimulates placental calcium transfer in humans.
- PTHrP may play a significant role in ensuring adequate calcium supply to the fetus.
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.