Kinetics and secretion of placental growth hormone around parturition

Abstract

Objective: During pregnancy, placental growth hormone (PGH) is secreted into the maternal circulation, replacing pituitary GH. It is controversial whether PGH levels decline during vaginal birth. After placental expulsion, PGH is eliminated from the maternal blood. GH binding protein (GHBP) and body mass index (BMI) influence GH kinetics, but their impact on PGH kinetics is unknown. The present study was undertaken to define the kinetics of PGH during vaginal delivery and Caesarian section and to relate these kinetics to GHBP and BMI. Design: A short term, prospective cohort study. Methods: Twelve women had repeated blood samples drawn during vaginal delivery. From 26 women undergoing planned Caesarian delivery (CS) repeated blood samples were withdrawn before, during and after the CS, allowing PGH half-life determination. Results: During vaginal delivery, median PGH values did not change before expulsion of the placenta, although individual fluctuations were seen. Clearance of PGH from the maternal circulation was best described by a two-compartment model. The initial half-life of serum PGH was (mean^S.D.) 5.8^2.4 min, and the late half-life was (median) 87.0 min (range: 25.1 -679.6 min). The late halflife was correlated to the pre-gestational BMI (r ¼ 0.39, P ¼ 0.047), but not to the serum GHBP concentration. Conclusions: Serum PGH did not decrease significantly during vaginal delivery. Elimination of PGH fitted a two-compartment model, with an estimated initial half-life of 5.8 min. The late phase serum half-life of PGH was related to BMI, suggesting a role for maternal fat mass in PGH metabolism.European Journal of Endocrinology 154 449-457

Decreased placental expression of hPGH, IGF-I and IGFBP-1 in pregnancies complicated by fetal growth restriction

“…Furthermore, the difference in the mode of delivery between the studied groups probably had no effect on the obtained results. No differences have previously been found in the concentration of hPGH in the maternal blood and the amniotic fluid in respect to caesarean section or vaginal delivery [53,54]. Despite the lack of data regarding the particular genes of this study, it has been shown that gene expression in a near term placenta is not significantly altered by labor, suggesting that the mode of delivery has no major implication in the interpretation of results of genomic studies on placenta [55].…”

Does the Physiological Acromegaly of Pregnancy Benefit the Fetus?

“…The elimination of circulating PGH can be described as the sum of two exponential curves: a rapid elimination phase with a median half-life of 5-6 min, and a slower elimination phase (half-life of 63.4 min) [19] ; thus, 65-89% of plasma PGH is cleared by 30 min after delivery [13,19] .…”

Growth hormone isoforms

“…The metabolic clearance of endogenous GH-V, estimated following expulsion of the placenta or cesarean section, appears to be somewhat faster than that of 22K-GH [87][88][89][90].…”