Normally, hCG (human chorionic gonadotropin) rises in the early stages of pregnancy, it can be determined in the blood and urine of a pregnant woman, in particular, pregnancy tests are based on this feature. Why donate blood for hCG during pregnancy and what level of hCG is the norm?
Why donate blood for hCG during pregnancy?
Determination of pregnancy hormones is a method that doctors use not so much to establish the presence of pregnancy, but rather to make sure that it is progressing, and in most cases for the diagnosis of ectopic pregnancy.
Human chorionic gonadotropin (hCG) is produced by the cells of the ovum, from which the placenta is then formed. Even in the absence of an embryo in the fetal egg (empty fertilized egg), the level of hCG in a woman can be increased. In a number of tumors of the ovaries and sometimes other organs, hCG may also be produced.
The peculiarity of hCG is that it consists of two subunits – alpha and beta:
the alpha-hCG subunit has the same structure as the analogous subunits of other hormones of the female body: luteinizing, follicle-stimulating, thyrotropic;
The subunit of beta-hCG has a unique structure and is characteristic of hCG pregnancy. Therefore, it is often in the serum that beta-hCG is determined.
This hormone must reach a certain concentration so that it can be detected in the serum. The level of beta-hCG is measured in thousandths of an international (international) unit per 1 ml of blood plasma (honey/ml, mIU / ml). It appears in the blood on the 7–8th day after conception, that is, on the 21–23rd day of the menstrual cycle, and in the urine on the 8–9th day after conception.
The level of hCG rises to the 10–12th week, after which its growth slows down, and then a new rise is observed after 22 weeks.
There are four main laboratory methods for the determination of beta-hCG. Each of them is designed for a specific minimum level of this hormone in the blood or urine of a woman. Radioimmunological method allows determining beta-hCG at 5 weeks of pregnancy. The immunoradiometric method can be applied in 4–5 weeks with a minimum hormone level of 150–15,000 mU/ml; This is a fast way to diagnose since it only takes 5–30 minutes to conduct it.
A fluoroimmunoassay is able to detect beta-hCG, which is only 1 mU/ml, and diagnose a 3.5-week pregnancy. However, such a highly sensitive method is not used to diagnose normal pregnancy, but more often to detect tumors that produce hCG (both in women and men), after miscarriages and abortions, and to detect an ectopic pregnancy.
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