Hormonal methods of research

In the relationship between the mother and fetus organisms, the placenta acts as a gland of internal secretion. In it, there are processes of synthesis, secretion and transformation of a number of hormones of the protein and steroid structure. In assessing the hormonal status of women, it should be borne in mind that in the early stages of pregnancy the function of all the endocrine glands increases, especially the production of the hormone of the yellow body - 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 fetal egg. In 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 placental hormone - chorionic gonadotropin (HG), which is a product of syncytiotrophoblast. In early pregnancy, the chorionic gonadotropin stimulates steroidogenesis in the yellow body. Modern methods of examining ... Ovary; in the second half of pregnancy - the synthesis of estrogens in the placenta. Chorionic gonadotropin is transported mainly to the mother's blood. In the blood of the fetus, its level is 10-20 times lower than in the blood of a pregnant woman. Chorionic gonadotropin is found in the blood of pregnant women immediately after implantation of the fetal egg. With the progression of pregnancy, its level in the blood rises, doubling every 1.7-2.2 days for 30 days. By 8-10 weeks, the maximum concentration in the blood, which varies between 60-100 IU / ml, is noted. In the second trimester of pregnancy, the content of chorionic gonadotropin in the blood is constantly low (10 IU / ml), and in the III trimester it increases somewhat. The excretion of chorionic gonadotropin with urine begins at 2 weeks of gestation and reaches the highest level in 10-12 weeks. Then there is a gradual decrease in the amount of chorionic gonadotropin in the urine. At 5-week pregnancy, 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 in 12 -13 weeks - 20,000 IU / liter. In subsequent terms, the level of chorionic gonadotropin in urine is in the range of 10,000-20,000 IU / L.

Great importance in the development of pregnancy and normal interrelations in the mother-placenta-fetus system is given to the placental lactogen (PL). This hormone has prolactin activity and the immunological properties of growth hormone, has a lactogenic and luteotropic effect, supporting steroidogenesis in the yellow ovary in the first trimester of pregnancy. The main biological role of placental lactogen is the regulation of carbohydrate and lipid metabolism and the enhancement of protein synthesis in the fetus. Placental lactogen is synthesized by trophoblast cells, identical in structure to the growth hormone. Its molecular weight is 21 000-23 000. The placental lactogen enters the mother's body, where it is quickly metabolized. Placental lactogen is detected in the mother's blood from 5-6 weeks of pregnancy. Placental lactogen practically does not penetrate to the fetus, in the amniotic fluid its level is 8-10 times lower than in the mother's blood. There was a direct relationship 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 placental and fetal status in terms of plasma levels in the blood and amniotic fluid.

Chorionic tissue and decidual membrane synthesize prolactin. This is evidenced by a high (10-100 times more 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 structural similarity to placental lactogen. Prolactin plays a role in the production of pulmonary surfactant of fetoplacental osmoregulation. Its content in the mother's blood serum increases progressively during pregnancy, especially at 18-20 weeks and before birth.

Progesterone is a sex steroid that has a placental origin. The biological role of this hormone in the development of pregnancy is unquestionable: progesterone is involved in the implantation of the fetal egg, suppresses uterine contractions, maintains the tone of the isthmic-cervical section, stimulates the growth of the uterus during pregnancy and takes part in steroidogenesis. Moreover, progesterone has the immunosuppressive action necessary for the development of the fetal egg (suppression of the rejection reaction). Progesterone is synthesized in syncytiotrophoblast in early pregnancy, however, the leading role of the placenta in the production of this hormone is revealed in 5-6 weeks. Until then, the main amount of the hormone is produced by the yellow body of pregnancy. By the 7-8 week of pregnancy, the concentration of progesterone doubles and continues to increase gradually to 37-38 weeks. Progesterone synthesized by the placenta comes mainly in the mother's blood, only 1 / 4-1 / 5 of it gets to the fetus. In the body of the mother (mainly in the liver) progesterone undergoes metabolic transformations and about 10-20% of it is excreted in the urine in the form of pregnanediol. The determination of the excretion of pregnanediol is important for diagnosing the threat of interruption and other disorders that accompany placental insufficiency, as well as for monitoring the effectiveness of treatment.

Steroid hormones of the placenta include estrogens (estradiol, estrone and estriol), produced by syncytiotrophoblast. Estrogens are rightfully referred to the hormones of the fetoplacental complex. At the beginning of pregnancy, when the mass of the trophoblast is small and the production of steroids in it is inadequate, the majority of estrogen is produced in the adrenal glands of the mother and the yellow body of the ovary. At 12-15 weeks, the production of estrogens increases sharply, and among the fractions, estriol begins to prevail. After the 20th week of pregnancy, the formation of estrogens is carried out mainly in the placenta with the active participation of the fetus. The main predecessor of estriol is produced in the tissues of the fetus (4 parts) and to a lesser extent in the adrenal glands of the mother (1 part). Since the secretion of estriol mainly depends on the androgenic progenitors produced in the adrenal glands of the fetus, the level of this hormone in the pregnant body reflects the condition not only of the placenta, but also of the fetus. In the first weeks of pregnancy, the excretion of estrogen in the urine and their content in the blood are at a level corresponding to the active phase of the yellow body outside of pregnancy. At the end of pregnancy, estrogen and estradiol in the urine is increased 100 times, and estriol - 500-1000 times compared with excretion before pregnancy. The determination of the level of excretion of estriol is of paramount importance for the diagnosis of abnormalities in the fetoplacental system. The diagnostic value of excretion of estriol is especially high in the second half of pregnancy. A significant decrease in the release of estriol in the last trimester of pregnancy indicates impairment of the fetus and functional insufficiency of the placenta. Alpha-fetoprotein (AFP) refers to glycoproteins; is formed in the yolk sac, the liver and the gastrointestinal tract of the fetus, where it enters the mother's blood. Probably, AFP is involved in the protection of fetal liver from the effects of maternal estrogens and plays a role in organogenesis. In the 18-20 weeks of pregnancy, its content in the mother's blood is on average less than 100 ng / ml, in 35-36 weeks - increases to 200-250 ng / ml, in the last weeks before childbirth again decreases. Optimal for the determination of AFP in the blood serum of the mother and amniotic fluid is the radioimmune method.

The course of pregnancy is judged by the activity of a number of enzymes, which depends on the condition of the placenta and fetus. To assess the function of the placenta use the definition in the blood serum of oxytocinase - an enzyme that inactivates oxytocin. The maximum activity of oxytocinase at a gestation period of 32 weeks is more than 6 units, during childbirth - 7.8 units. A certain role is played by the change in the activity of thermostable alkaline phosphatase (TCF), a placenta specific enzyme. This test is considered the most sensitive for establishing placental dysfunction. The lifetime of TCB in serum is 3.5 days. The diagnostic value is not so much the absolute value of TC activity, as its share in the total phosphatase activity of the blood. With a satisfactory state of the placenta, the TCF makes up more than 50% of the total activity of the AF. With the diagnostic purpose, the activity of phosphokinase, cathepsins, hyaluronidase is also used, the content of which sharply increases for abnormalities in the placenta.

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]