How long after the fertilized egg implants does HCG begin to be secreted?

Patient's question:

No

Doctor's answer:

HCG is produced by trophoblastic transitional cells and syncytiotrophoblast cells. In the first 8 weeks of pregnancy, it multiplies rapidly to maintain the pregnancy. After about 8 weeks of gestation, HCG gradually declines until it reaches a relatively stable level around 20 weeks.