Hormonal research methods

In the relationship between the mother and fetus, the placenta acts as an endocrine gland. It is where the processes of synthesis, secretion and transformation of a number of hormones of protein and steroid structure occur. When assessing the hormonal status of a woman, it should be taken into account that in the early stages of pregnancy, the function of all endocrine glands increases, especially the production of the corpus luteum hormone - progesterone. Already in the preimplantation period at the blastocyst stage, the germ cells secrete progesterone, estradiol and chorionic gonadotropin, which are of great importance for the implantation of the ovum. During the process of organogenesis of the fetus, the hormonal activity of the placenta increases, and throughout the pregnancy, the placenta secretes a large number of hormones.

In the development of pregnancy, an important role is played by the placental hormone - human chorionic gonadotropin (hCG), which is a product of the syncytiotrophoblast. In the early stages of pregnancy, human chorionic gonadotropin stimulates steroidogenesis in the corpus luteum Modern research methods... of the ovary; in the second half of pregnancy - estrogen synthesis in the placenta. Human chorionic gonadotropin is transported mainly into the mother's blood. In the blood of the fetus, its level is 10-20 times lower than in the blood of the pregnant woman. Human chorionic gonadotropin is found in the blood of pregnant women immediately after implantation of the ovum. As pregnancy progresses, its level in the blood increases, doubling every 1.7-2.2 days for 30 days. By the 8th-10th week, its maximum concentration in the blood is noted, which varies within 60-100 IU/ml. In the second trimester of pregnancy, the content of human chorionic gonadotropin in the blood is constantly at a low level (10 IU/ml), and in the third trimester it increases slightly. The excretion of human chorionic gonadotropin with urine begins from the 2nd week of pregnancy and reaches its highest level at 10-12 weeks. Then there is a gradual decrease in the amount of human chorionic gonadotropin in the urine. At 5 weeks of pregnancy, human chorionic gonadotropin is excreted in the urine in the amount of 500-1500 IU/l, at 7-8 weeks - 1500-2500 IU/l, at 10-11 weeks - 80,000-100,000 IU/l, and at 12-13 weeks - 20,000 IU/l. In the following periods, the level of human chorionic gonadotropin in the urine is within 10,000-20,000 IU/l.

Placental lactogen (PL) plays a major role in the development of pregnancy and normal relationships in the mother-placenta-fetus system. This hormone has prolactin activity and immunological properties of growth hormone, has a lactogenic and luteotropic effect, supporting steroidogenesis in the corpus luteum of the ovary in the first trimester of pregnancy. The main biological role of placental lactogen is to regulate carbohydrate and lipid metabolism and enhance protein synthesis in the fetus. Placental lactogen is synthesized by trophoblast cells and is structurally identical to growth hormone. Its molecular weight is 21,000-23,000. Placental lactogen enters the mother's body, where it is quickly metabolized. Placental lactogen is detected in the mother's blood as early as the 5th-6th week of pregnancy. Placental lactogen practically does not penetrate to the fetus, its level in amniotic fluid is 8-10 times lower than in the mother's blood. A direct relationship was noted between the level of placental lactogen in the mother's blood and in the amniotic fluid, between the hormone content in the blood and the weight of the fetus and placenta, which served as the basis for assessing the state of the placenta and fetus by the level of PL in the blood and amniotic fluid.

The chorionic tissue and decidua synthesize prolactin. This is evidenced by the high (10-100 times higher than in the blood) content of this hormone in the amniotic fluid. During pregnancy, in addition to the placenta, prolactin is secreted by the pituitary gland of the mother and fetus. The physiological role of prolactin is determined by its structural similarity to placental lactogen. Prolactin plays a certain role in the production of pulmonary surfactant of fetoplacental osmoregulation. Its content in the mother's blood serum progressively increases during pregnancy, especially at 18-20 weeks and before labor.

Progesterone is a sex steroid of placental origin. The biological role of this hormone in the development of pregnancy is undeniable: progesterone is involved in the implantation of the fertilized egg, suppresses uterine contractions, maintains the tone of the isthmic-cervical region, stimulates the growth of the uterus during pregnancy and participates in steroidogenesis. Moreover, progesterone has an immunosuppressive effect necessary for the development of the fertilized egg (suppression of the rejection reaction). Progesterone is synthesized in the syncytiotrophoblast already in the early stages of pregnancy, but the leading role of the placenta in the production of this hormone is revealed at 5-6 weeks. Before this period, the main amount of the hormone is produced by the corpus luteum of pregnancy. By the 7-8 week of pregnancy, the concentration of progesterone doubles and continues to gradually increase by the 37-38 week. Progesterone synthesized by the placenta enters mainly into the mother's blood, only 1/4-1/5 of it gets to the fetus. In the mother's body (mainly in the liver), progesterone undergoes metabolic transformations and about 10-20% of it is excreted in the urine as pregnanediol. Determining the excretion of pregnanediol is important for diagnosing the threat of miscarriage and other disorders that accompany placental insufficiency, as well as for monitoring the effectiveness of treatment.

Placental steroid hormones also include estrogens (estradiol, estrone, and estriol) produced by the syncytiotrophoblast. Estrogens are rightfully considered hormones of the fetoplacental complex. At the beginning of pregnancy, when the trophoblast mass is small and steroid production in it is insufficient, the main amount of estrogens is produced in the mother's adrenal glands and the corpus luteum of the ovary. At 12-15 weeks, estrogen production increases sharply, and estriol begins to prevail among the fractions. After the 20th week of pregnancy, estrogen formation occurs mainly in the placenta with the active participation of the fetus. The main precursor of estriol is produced in the tissues of the fetus (4 parts) and to a lesser extent in the mother's adrenal glands (1 part). Since estriol secretion depends mainly on androgen precursors produced in the fetal adrenal glands, the level of this hormone in the pregnant woman's body reflects the condition of not only the placenta, but also the fetus. In the first weeks of pregnancy, estrogen excretion in the urine and their content in the blood are at the level corresponding to the active phase of the corpus luteum outside of pregnancy. At the end of pregnancy, the content of estrone and estradiol in the urine increases by 100 times, and estriol - by 500-1000 times compared to excretion before pregnancy. Determination of the level of estriol excretion is of primary importance for diagnosing disorders in the fetoplacental system. The diagnostic value of the estriol excretion level is especially high in the second half of pregnancy. A significant decrease in estriol excretion in the last trimester of pregnancy indicates deterioration of the fetus and functional insufficiency of the placenta. Alpha-fetoprotein (AFP) is a glycoprotein; is formed in the yolk sac, liver and gastrointestinal tract of the fetus, from where it enters the mother's blood. Probably, AFP is involved in protecting the fetus's liver from the effects of maternal estrogens and plays a certain role in organogenesis. At 18-20 weeks of pregnancy, its content in the mother's blood is on average less than 100 ng/ml, at 35-36 weeks it increases to 200-250 ng/ml, and in the last weeks before birth it decreases again. The radioimmune method is optimal for determining AFP in the mother's blood serum and amniotic fluid.

The course of pregnancy is also assessed based on the activity of a number of enzymes, which depends on the condition of the placenta and fetus. To assess placental function, oxytocinase, an enzyme that inactivates oxytocin, is measured in the blood serum. The maximum activity of oxytocinase at 32 weeks of pregnancy is more than 6 U, and during labor - 7.8 U. A certain role is played by changes in the activity of thermostable alkaline phosphatase (TSAP), an enzyme specific to the placenta. This test is considered the most sensitive for determining placental dysfunction. The lifetime of TSAP in the blood serum is 3.5 days. The absolute value of TSAP activity is not as important as its share in the total phosphatase activity of the blood. With a satisfactory condition of the placenta, TSAP accounts for more than 50% of the total ALP activity. For diagnostic purposes, the determination of the activity of phosphokinase, cathepsins, and hyaluronidase, the content of which increases sharply in case of disturbances in the placenta, is also used.

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