Table 1 The biological functions of the isoforms of hCG.

   A. hCG

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.

   B. Hyperglycosylated hCG

1. Stimulates implantation by invasion of cytotrophoblast cells as occurs at implantation of pregnancy, blocks apoptosis and growth and malignancy of choriocarcinoma cells.

2. Stimulates growth of placenta and malignant placenta by promoting growth of cytotrophoblast cells

   C. Free β-subunit

1. Blockage of apoptosis in no-trophoblastic malignancies, promotion of growth and malignancy

   D. Pituitary hCG

1. Seemingly mimics LH functions, promoting follicular growth, meiosis, stigma formation, ovulation, luteogenesis and promoting progesterone production.