Human Chorionic Gonadotropin

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 teratogenic to 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.

Links: Placenta Development | Week 2

Functions

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

Levels peak at 8 to 10 weeks of pregnancy, then decline and are lower for rest of pregnancy

0-1 week: 0-50 mIU/ml 


1-2 weeks: 40-300 mIU/ml

3-4 weeks: 500-6,000 mIU/ml

1-2 months: 5,000-200,000 mIU/ml

2-3 months: 10,000-100,000 mIU/ml

2nd trimester: 3,000-50,000 mIU/ml

3rd trimester: 1,000-50,000 mIU/ml

Non-pregnant females: <5.0 mIU/ml Postmenopausal females: <9.5 mIU/ml

Protein

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.

References

Search Pubmed

Search Pubmed: Human Chorionic Gonadotropin | hCG

Search Bookshelf: 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. (2024, April 16) 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 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G