hCG physiology

• hCG is produced during pregnancy, primarily by the placental syncytiotrophoblast.
• The role of hCG is to:
  • Stimulate progesterone secretion by the corpus luteum during the first 3–6 weeks of gestation to maintain pregnancy
    • Prior to pregnancy, LH stimulates corpus luteal progesterone secretion.
    • After the luteal placental shift, the placenta produces progesterone.
  • Promote uterine angiogenesis
  • Promote myometrial stability, preventing contractions prior to labor
  • Support immune tolerance to the growing embryo
• Structure
  • α-subunit: common to hCG, FSH, LH, and TSH
  • β-subunit
    • Specific to hCG
    • Pregnancy tests generally detect hCG through antibodies to the β-subunit.

Types of pregnancy tests