Human Chorionic Gonadotropin

Embryology - 5 Dec 2023        Expand to Translate
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Introduction

File:Pregnancy test

Human chorionic gonadotropin (hCG, or human chorionic gonadotrophin) is a placental hormone initially secreted by cells (syncitiotrophoblasts) from the implanting conceptus during week 2, supporting the ovarian corpus luteum, which in turn supports the endometrial lining and therefore maintains pregnancy.

The hormone can be detected in maternal blood and urine and is the basis of many pregnancy tests. The protein has many other roles including stimulating the onset of fetal gonadal steroidogenesis, and high levels have been found to be a teratogen to the fetal gonadal tissues.

Other potential cellular sources can include: hyperglycosylated hCG produced by cytotrophoblast cells, free beta-subunit made by multiple primary non-trophoblastic malignancies, and pituitary hCG made by the gonadotrope cells of the anterior pituitary.

A member of the glycoprotein hormone family that includes the pituitary hormones: luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid-stimulating hormone (TSH).

Some Recent Findings

Human Chorionic Gonadotropin Induces Human Macrophages to Form Intracytoplasmic Vacuoles Mimicking Hofbauer Cells in Human Chorionic Villi The most characteristic morphological feature of macrophages in the stroma of placental villi, known as Hofbauer cells, is their highly vacuolated appearance. They also show positive immunostaining for human chorionic gonadotropin (hCG)." Serum biomarkers for predicting pregnancy outcome in women undergoing IVF "This study was performed to assess the prognostic value of serum hCG, progesterone, and inhibin A levels measured at 11 days post-ET for predicting pregnancy outcome in women participating in IVF. Between May 2005 and April 2008, sera were obtained from 70 infertile women who underwent IVF-ET at 11 days post-ET and stored. HCG, progesterone, and inhibin A levels were measured by commercial enzyme-linked immunosorbent assay kits. The predictive accuracy of hCG, progesterone, and inhibin A levels for establishment of intrauterine pregnancy and ongoing pregnancy was calculated by receiver-operating characteristic curve analysis. For the prediction of intrauterine and ongoing pregnancy, serum hCG was better than progesterone and inhibin A. The predictive performance of progesterone and inhibin A was similar. The serum progesterone and inhibin A levels were significantly correlated each other (r=0.915, p=0.010)."

More recent papers

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Functions

Trophoblast hCG function

1. Promotion of corpus luteal progesterone production
2. Angiogenesis of uterine vasculature
3. Cytotrophoblast differentiation
4. Immuno-suppression and blockage of phagocytosis of invading trophoblast cells
5. Growth of uterus in line with fetal growth
6. Quiescence of uterine muscle contraction
7. Promotion of growth and differentiation of fetal organs
8. Umbilical cord growth and development
9. Blastocysts signals endometrium prior to implantation
10. hCG in sperm and receptors found in fallopian tubes suggesting pre-pregnancy communication
11. hCG receptors in adult brain hippocampus, hypothalamus and brain stem, may cause pregnancy nausea and vomiting
12. hCG and implantation of pregnancy, hCG stimulates metalloproteinases of cytotrophoblast cell

Function Data from Table 1

Maternal Blood Levels

Maternal Blood - Human Chorionic Gonadotrophin (hCG) Levels

Pregnancy
Time (GA) weeks	Levels (mIU/mL)
0 - 1 weeks	0 - 50
1 - 2 weeks	40 - 300
3 - 4 weeks	500 - 6,000
1 - 2 months	5,000 - 200,000
2 - 3 months	10,000-100,000
second trimester	3,000 - 50,000
third trimester	1,000 - 50,000
Non-pregnant	< 5.0
Post-menopausal	< 9.5
Pregnancy test - greater than 20 mIU/mL (milli-international units per milliliter) is a positive result.   Levels peak at 8 to 10 weeks of pregnancy, then decline and are lower for rest of pregnancy.

Protein

Trophoblast cell hCG glycosylation

Human 5 protein forms:

1. hCG
2. sulfated hCG
3. hyperglycosylated hCG
4. hCG free beta
5. hyperglycosylated free beta

The molecular weight of hCG is approximately 36,000 (36 KDa) for the α-subunit and a β-subunit that are held together by both non-covalent hydrophobic and ionic interactions.

Corpus Luteum

Section through the middle of a human ovary at mid-luteal phase of the menstrual cycle after ovulation. (unlabeled image).

• corpus luteum (white ring) shown at top left of ovary. Note the size and colour of the the corpus luteum ("yellow body") compared to the ovary and other internal structures. If implantation and pregnancy occurs, then hCG would stimulate an increase in size and hormonal function during the early pregnancy.
  • white asterisks - possible older corpora lutea remnants.

• corpus albicans (white arrow) shown at the bottom right of the ovary. Note the size and colour of the corpus albicans ("white body") compared to the corpus luteum and ovary. The corpus albicans is the degenerating non-functional form of the corpus luteum that "develops" from it if implantation and pregnancy do not occur.
  • black asterisks - possible older corpora albicantia remnants.

Black arrows show the approximate cortex and medullary regions of the ovary.

Ovary corpus luteum histology.

Genital Development

Placental secreted hCG has leutenizing hiormone-like effects that can effect genital development, stimulating testosterone production from the testes of the male fetus and subsequent development of male genital system.

References

Search Pubmed

Search Pubmed: Human Chorionic Gonadotropin | hCG

Search Bookshelf: Human Chorionic Gonadotropin

Search OMIM: Human Chorionic Gonadotropin

External Links

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• NIH The History of the Pregnancy Test

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Cite this page: Hill, M.A. (2023, December 5) Embryology Human Chorionic Gonadotropin. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Human_Chorionic_Gonadotropin

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© Dr Mark Hill 2023, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G