HCG is a glycoprotein secreted by the trophoblast cells of the placenta. It
is composed of glycoproteins of alpha and beta dimers. The function stimulates
the corpus luteum, is advantageous to the estrogen and the progesterone
continuous secretion, promotes the uterus decidua to form, causes the placenta
to grow the mature. HCG changes at different stages. After embryo implantation,
HCG starts to be secreted as trophoblast cells develop. The amount of normal
pregnancy is small at the beginning, peaking at 8-10 weeks and then gradually
declining. After 14 weeks of gestation (100 days), HCG decreased significantly.
HCG was also higher in twin or multiple pregnancies than in single pregnancies.
Significance of HCG 1. Differential diagnosis of normal and abnormal pregnancy.
2. Diagnosis and treatment of abortion. 3. High levels of HCG in urine, ranging
from 100,000 to millions of ius, can occur in malignant hydatidiform mole,
choriocarcinoma, and testicular teratoma in men. 4. Others: HCG changes in
pregnancy toxemia, which is often on the high side; HCG levels increased during
multiple pregnancies.
Blood HCG reference value (mIU/ml) unit conversion: 1IU=1000mIU
3-4 weeks: 9-130
Gestation 4--5 weeks: 75--2600
Pregnancy 5--6 weeks: 850--208003
Pregnancy 6--7 weeks: 4000--100200
Pregnancy 7--12 weeks: 11,500 -- 289,000
Pregnancy 12--16 weeks: 18,300 -- 137,000
Pregnancy 16--29 weeks: 1400--53000
Pregnancy 29--41 weeks: 940-- 60,000
HCG increases rapidly in serum in the first trimester of pregnancy,
doubling in about 1.7-2 days, reaching the highest serum concentration at 8-10
weeks of gestation, and then rapidly decreasing after 12 weeks, and then
maintaining a certain level.
If HCG increases by more than 66% every two days, an intrauterine pregnancy
can be diagnosed. If the increase is less than 66 percent, the odds of ectopic
or intrauterine pregnancy dysplasia are high. For ectopic pregnancy, due to the
thin muscle layer of fallopian tube and poor blood supply, the secretion of HCG
is very low and the upward appreciation is less than 50% within 48 hours.