Human chorionic gonadotropin (hCG) is a glycoprotein secreted by the trophoblast cells of the placenta and is the most commonly used pregnancy test hormone. The main function is to stimulate the corpus luteum, which is conducive to the continuous secretion of estrogen and progesterone, so as to promote the formation of decidua of the uterus and make the placenta grow and mature. Once the embryo is implanted, the trophoblasts will begin to secrete hCG, so pregnancy can be judged by the hCG value in the blood or urine.
Do you know the role of hCG human chorionic gonadotropin
A complete hCG is composed of glycoproteins of α and β dimers: α-subunit is shared by anterior pituitary hormones, and its composition and structure are consistent with human pituitary TSH, LH, and FSHa subunits, so the determination of hCG is the same as the above The three hormones have cross-reactions.
β-subunit is specific for hCG. Therefore, β-subunit determines hCG and biological and immunological characteristics. The determination of β-hCG can reduce cross-reaction and accurately reflect the level of hCG in blood and urine.
hCG changes in different periods
After the embryo is implanted, hCG will begin to secrete as the trophoblasts develop. The amount is small at the beginning of a normal pregnancy, and reaches a peak at 8-10 weeks of gestation, and then gradually decreases. After 14 weeks (100 days) of pregnancy, hCG decreased significantly. In twin (multiple) pregnancies, the hCG value is also higher than that of single pregnancies. The hCG examination is of great significance for the diagnosis of early pregnancy, and has certain value for the diagnosis, identification and course observation of diseases such as pregnancy-related diseases and trophoblastic tumors.
Diagnose early pregnancy
The hCG value after pregnancy varies from person to person, and there is no clear normal value range. Blood hCG can rise to more than 2500IU/L on 35-50 days of pregnancy. The highest peak is reached in 60-70 days. In the case of multiple pregnancy, urine hCG is often higher than that in singleton pregnancy. In pregnancy induced by gonadotropin stimulation, it must be noted that the pregnancy can only be confirmed after 10 times the half-life of exogenous hCG administration.
Patients before 7 weeks of pregnancy can determine the gestational age by analyzing hCG of at least 2 blood samples. These 2 blood samples should be separated by 2-7 days, because hCG doubles every 2 days during pregnancy. A linear relationship between the logarithm of the hCG concentration and the number of days of measurement can be obtained.
Judgment of abnormal pregnancy and placental function
Ectopic pregnancy: Under normal circumstances, the serum hCG concentration doubles every 1.7-2.5 days. When trophoblast cells in the normal uterine cavity are underdeveloped, hCG rises slowly. However, if the embryo is underdeveloped or has no implantation, if this growth rate is not reached, it indicates that a miscarriage or an ectopic pregnancy is more likely to occur. But even if hCG grows as expected, it is necessary to refer to the E2 and P values for preliminary judgment. If the E2 and P values are very low, the possibility of ectopic pregnancy should be considered. The positive predictive value of excluding ectopic pregnancy with normal rise of hCG was 94.7%.
Another reliable method is to compare the ultrasound results with the hCG concentration. When the hCG reaches 1000-2000IU/L or more, the vaginal ultrasound should be able to identify the intrauterine gestational sac; when the hCG must reach 6500IU/L, the abdominal ultrasound can identify the intrauterine gestational sac. If this is not the case, an ectopic pregnancy should be suspected. Of course, you should also refer to the time of the next menstruation or embryo transfer. If the time is too short, even if the hCG value is high, the gestational sac may not be seen by ultrasound.
Diagnosis and treatment of miscarriage: When hCG rises or drops at a slow and low rate, the possibility of miscarriage should be considered, but treatment should be paid attention to. hCG represents the vitality of nourishing embryos. Even if hCG rises, it cannot be represented. Embryos must survive, and pregnancy-preserving treatments can only increase progesterone levels, and cannot make bad embryos "better".
Incomplete abortion If there is still placental tissue remaining in the uterus, the hCG test can still be positive for a long time, but for a complete abortion, hCG turns negative within a certain period of time. For example, the serum hCG should be lower than 1000IU/L on the 4th day after delivery or 13 days after the artificial abortion, and the serum hCG should return to normal on the 9th day after delivery or 25 days after the artificial abortion. If this situation is not met, the possibility of abnormality should be considered.
Trophoblastic tumor diagnosis and treatment monitoring
In patients with gestational trophoblastic tumors such as hydatidiform mole and choriocarcinoma, hCG in hematuria is significantly higher than that in normal pregnancy. The diagnosis can be made by combining B-ultrasound and medical history.
Luteinizing hormone cross-reaction
Other causes such as menopause, ovulation, and bilateral oophorectomy, which lead to increased luteinizing hormone, can also affect blood hCG, leading to increased hCG during examination. Because the composition of the alpha peptide chain of LH and hCG is the same, the pregnancy test using anti-hCG antibody is positive. At this time, it can be identified by the monoclonal two-point enzyme immunoassay of beta-hCG.
"In recent years, it has been discovered that certain malignant tumors, such as pancreatic cancer, stomach cancer, liver cancer, breast cancer, lung cancer, etc., can also increase hCG in the blood. Therefore, hCG can be regarded as one of the cancer markers. However, it is necessary to comprehensively analyze and judge the clinical situation and other inspection results.
The best time for hCG (human chorionic gonadotropin) test
Blood hCG test determines whether a woman is pregnant or not by measuring the hCG value in the woman's blood. Compared with traditional urine hCG, blood hCG is more sensitive and accurate, with smaller errors, and can advance the detection time. In order to detect the accuracy of pregnancy as soon as possible, general doctors recommend a blood hCG early pregnancy test. The "quantitative" examination of hCG value through blood can be more sensitive and accurate in responding to pregnancy than ordinary early pregnancy test paper "qualitative" detection of urine, and its accuracy rate is more than 99%.
When menstruation is delayed, or menstrual volume and traits are abnormal, you must go to the hospital for blood hCG examination, B-ultrasound examination, and urine test to confirm whether you are really pregnant. If you are really pregnant, make sure Whether it is intrauterine pregnancy or ectopic pregnancy, and then do the corresponding treatment. Don't call the shots without authorization, just rely on some symptoms to determine that you are pregnant. Don't think that as long as you "have menstruation", you are not pregnant. Sometimes an abnormal pregnancy may cause vaginal bleeding at the time of menstruation. If you mistake it for normal menstruation, it will delay the diagnosis and treatment of some diseases.
After conception, the β-hCG in the bleeding can be measured from the 9th-11th day of the fertilization day, and it will increase rapidly in the first 8 weeks of pregnancy to maintain pregnancy. After about 8 weeks of gestation, hCG is at a plateau and even gradually decreases until it reaches a relative stability at about 20 weeks. In general, urine hCG tests such as early pregnancy test strips are usually tested after one week of menopause, while blood hCG early pregnancy tests are usually tested one or two days after menopause. This can advance the time to confirm pregnancy, so that pregnancy can be detected earlier. Make corresponding countermeasures.