HCG, human chorionic gonadotrophin, is a glycoprotein secreted by the trophoblast cells of the placenta, which is composed of glycoproteins of alpha and beta dimers. HCG test strips are the most widely used test tool to detect human chorionic gonadotrophin. However, the alpha-subunit is common to anterior pituitary hormones. The β-subunit is specific to HCG. Complete HCG is produced entirely by the syncytial trophoblast of the placental chorionic villi.
Normal reference values.
(1) Normal values of blood HCG <10 μg/L.
(2) Normal value of β-HCG <3.1 μg/L.
HCG enters maternal blood around the sixth day after fertilization and proliferates rapidly until the eighth week of pregnancy, then slowly decreases in concentration until the 18th to 20th week, then remains for about 10 days and begins to decline (but remains above normal levels). Generally intact hCG levels are elevated to at least 2.5 MoM to be associated with Down’s syndrome. In contrast, actual intact hCG levels in the maternal blood of DS patients average only 1.3 MoM, which does not clearly identify DS patients.
The hCG-related molecules used for DS screening are free b-hCG and high-glucose hCG (H-hCG). h-hCG-related molecules are sensitive for screening Down syndrome and can be sampled in urine. h-hCG concentrations in the plasma of mothers of children with DS are 9.9-fold higher than those of non-infected pregnant women.
Free b-hCG is now the only known marker that can be used for both phase I and phase II screening. The mean level of free b-hCG in maternal blood for DS syndrome is 1.9 MoM, compared to 1.0 MoM in healthy maternal blood. hCG-related molecule levels are also associated with fetal sex, with female infants having significantly higher hCG levels than male infants.
Intact HCG is produced entirely by the syncytial trophoblast of the placental chorionic villi. Its main function is to stimulate the corpus luteum, which facilitates the continuous secretion of estrogen and progesterone to promote the formation of the uterine meconium and the growth and maturation of the placenta. The modern belief is that HCG is produced by trophoblast transitional cells and syncytiotrophoblast cells. HCG secretion begins about 6 days after fertilization and reaches a peak on day 60-70. It increases rapidly in value during the first 8 weeks of pregnancy to maintain the pregnancy. After about 8 weeks of gestation, HCG gradually decreases until it reaches relative stability at about 20 weeks.
The absolute value of serum HCG varies greatly from one pregnancy to another and from one person to another, so it is not comparable and can only be compared with itself.
General non-pregnant women: blood HCG <100IU/L
During the first 3 months of pregnancy, HCG level doubles approximately every 2.2±0.5 days.
Urine-HCG (HCG semi-quantitative method).
<25 IU/L in non-pregnant women.
40 days of gestation >5000IU/L,
60-70 days of pregnancy >;(8-32)×104IU/L (the highest urinary HCG level in the early morning, close to the serum level).
Serum HCG levels during normal pregnancy.
Gestational weeks HCG (IU/L)
0.2-1 week 5-50
1-2 weeks 50-500
2-3 weeks 100-5000
3-4 weeks 500-10000
4-5 weeks 1000-50,000
5-6 weeks 10,000-100,000
6-8 weeks 15000-200000
2-3 months 10000-100000
Human chorionic gonadotropin (hcg) conversion time.
8 weeks after clearance of gravida, 2 weeks after miscarriage, 1 week after full-term delivery, and persistently positive if there is residual.
The hcg value of ectopic pregnancy, ectopic pregnancy is a blood HCG test that may be lower than the level of a normal intrauterine pregnancy, but will be higher than the HCG level of a non-pregnant pregnancy. The left adnexal mass may be an inflammatory mass or an ectopic embryonic tissue. The hcg value of ectopic pregnancy, when the embryo is alive or the trophoblast is viable, the syncytial cells secrete hCG and the pregnancy test may be positive. Since the level of hCG in ectopic pregnancy is lower than that in normal pregnancy, the general method of hCG determination has a low positive rate, and the more sensitive beta-hCG radioimmunoassay or monoclonal antibody enzyme labeling method must be used for detection.
HCG clinical applications
1.Diagnosis of early pregnancy.
2.In ectopic pregnancy, HCG can still be positive 3 days after uterine bleeding, and can be used to differentiate from other acute abdominal diseases, but its positive rate is only about 60%.
3.HCG test can still be positive in case of incomplete miscarriage, and change from chronic to negative in case of complete miscarriage or stillbirth.
4.It is used to judge the situation after delivery or abortion. If it does not recover within a certain period of time, abnormalities should be considered.
5.It can be significantly increased in cases of staphyloma, malignant staphyloma, chorioepithelial carcinoma and testicular teratoma.
6.It should be used for postoperative observation of tumor.
7.Other endocrine diseases such as pituitary disease, hyperthyroidism, ovarian tumor, uterine cancer, stomach cancer, liver cancer, etc. may also be increased.
HCG measurement precautions
1, identify normal and abnormal pregnancy: HCG changes during pregnancy is a bimodal curve, according to the normal HCG concentration changes, if the first HCG is within the normal range, 79% of people can have a full-term pregnancy, if the first HCG is below normal, 92% of pregnancy failure.
2, diagnosis and treatment of miscarriage: incomplete miscarriage, there is still placental tissue remaining in the uterus, HCG qualitative positive, complete miscarriage or stillbirth when HCG 2, negative, such as HCG below 2500 U/L and gradually declining, there is a possibility of miscarriage or stillbirth; when it drops to 600 U/L, it is inevitable miscarriage, such as HCG in urine constantly declining, indicating that birth control is ineffective, and vice versa, suggesting successful birth control. Four days after delivery or 13 days after abortion, serum HCG should return to normal. If it does not meet this condition, abnormal possibility should be considered.
3.In case of malignant gravida, chorioepithelial carcinoma and male testicular teratoma, the urinary HCG level is very high, up to 100,000 to millions of international units.
4, Other: HCG varies in pregnancy toxemia, often high; HCG content increases in multiple pregnancies.