Gonadotropin-Releasing Hormone Increases Serum Human Chorionic Gonadotropin in Pregnant Women.

Abstract

Abstract. Hypothalamic decapeptide, gonadotropin-releasing hormone (GnRH) has been found to stimulate human chorionic gonadotropin (hCG) secretion by trophoblast cells in vitro. To determine the biological effect of GnRH on the release of hCG in vivo, we studied the effect of the administration of GnRH on the serum levels of human chorionic gonadotropin (hCG) during pregnancy. Serum hCG levels were measured before and 15, 30, and 60 min after the intravenous administration of 100 µg of GnRH to 22 volunteers with normal pregnancy. Nine of the 12 (75%) women responded to GnRH in the first trimester, while only 1 of the 5 women (20%) responded to GnRH in the second trimester. None of the 5 women tested in the third trimester showed a significant response of hCG to the injection of GnRH. The average increase in hCG during the first, second and third trimester was 160.7± 13.5%,111.0±7.4% and 95.0±2.3%, respectively (mean ± SEM). Whereas the pregnant courses of all the cases were uneventful and normal, other abnormal pregnancies were also investigated with informed consents. Three patients with missed abortions also showed a significant response of hCG to GnRH (increase: 136.7±8.5%) when GnRH was administered before curettage of the uterine cavity. However, 4 patients with unruptured ectopic pregnancies did not respond to GnRH stimulation. These findings indicate that GnRH can stimulate the release of hCG by the placenta in vivo, consistent with the previous in vitro study, while the responsiveness depends on gestational age and the implantation site.

Gonadotropin-Releasing Hormone-Induced Elevation of Serum hCG in Choriocarcinoma: A Case Report.

“…This means that hCG has the ability to be stored if the cell has storage granules. No large dense-core storage granules have been identified in placenta and choriocarcinoma cell lines [20], but stimulation of hCG release by GnRH and KCl from choriocarcinoma cells [15] and an increase in serum hCG shortly after GnRH administration in pregnant women [16] support the idea that there may be a small number of granules in placenta and malignant trophoblastic tissues.…”

“…In pregnancies, the implantation site affected the response of hCG to GnRH [16]. Patients with tubal pregnancy did not respond to GnRH, in contrast to normal pregnancy or missed abortion where a fertilized egg was implanted in the uterus.…”

“…Recently Iwashita et al [16] reported that GnRH stimulates the release of hCG from the placenta in vivo, although the responsiveness depends on gestational age and the implantation site, but few data in vivo on GnRH-induced alterations in the secretion of hCG has been shown in patients with GTD.…”

Human Placenta as a Source of Neuroendocrine Factors

“…Abundant expression of both hormone and receptor is observed in the cyto-and syncytiotrophoblast, where they are localized in identical cells [25]. Placental GnRH is likely to be one of the paracrine regulators of hCG secretion, as suggested by evidence from in vivo and in vitro experiments [26,27]. Administration of GnRH to pregnant women elicits a significant increase in hCG in the first trimester, a response seldom observed in the third trimester [27].…”

“…Placental GnRH is likely to be one of the paracrine regulators of hCG secretion, as suggested by evidence from in vivo and in vitro experiments [26,27]. Administration of GnRH to pregnant women elicits a significant increase in hCG in the first trimester, a response seldom observed in the third trimester [27]. This different sensitivity may be explained by the downregulation of GnRH receptors in the term placenta [28].…”