Placental lactogen in the blood

Reference values (norm) for placental lactogen concentration: absent in blood serum in men and non-pregnant women; during pregnancy from 5 to 38 weeks - 0.5-11 μg/ml (23-509 nmol/l).

Placental lactogen or placental somatomammotropin is a glycoprotein with a molecular weight of approximately 19,000. It is synthesized by the syncytiotrophoblast from the early stages of pregnancy, and its content in the blood during a physiologically proceeding pregnancy increases. The maximum concentration of placental lactogen is recorded at the 36-37th week of pregnancy, then it stabilizes, and decreases before labor. The concentration of placental lactogen is highly variable, individual and directly depends on the weight of the fetus and the number of placentas (in multiple pregnancies ). Placental lactogen enters the body of the pregnant woman, where it is quickly metabolized (half-life is from 11 to 30 minutes). The short half-life, the absence of a daily rhythm of secretion and the presence of a single source of its synthesis allow it to be used as a direct indicator of placental functioning. Placental lactogen practically does not penetrate to the fetus, its level in amniotic fluid is 8-10 times lower than in the blood of the pregnant woman. In its properties, it is similar to growth hormone, but during pregnancy its production exceeds the secretion of growth hormone by 100 times. Placental lactogen stimulates the mobilization of fatty acids, has a lactotropic and luteotropic effect, inhibits cellular immunity, actively affects metabolism (promotes glucose consumption in the fetus's body, reduces protein synthesis in the pregnant woman, which significantly increases the supply of amino acids that the fetus uses for its formation). Placental lactogen is also an insulin antagonist, plays an important role in the maturation and development of the mammary glands during pregnancy and in their preparation for lactation. In addition, like prolactin, it supports the work of the corpus luteum of the ovaries during pregnancy, promotes an increase in the secretion of progesterone by the corpus luteum.

In the 1st trimester of pregnancy, with the development of placental insufficiency, the level of placental lactogen is significantly reduced. Extremely low values of its concentration in the blood are detected on the eve of fetal death and 1-3 days before spontaneous abortion. In later stages of pregnancy, a decrease in the concentration of placental lactogen is detected in placental insufficiency and chronic fetal hypoxia. At the same time, its content in the blood fluctuates within a wide range, but in most pregnant women it is significantly below normal. With placental insufficiency, the content of placental lactogen in the blood serum decreases by 50%, and with fetal hypoxia - almost 3 times. The concentration of placental lactogen decreases in hypertension, late gestosis. Indications for the study of placental lactogen: diagnosis of placental insufficiency, hypoxia and fetal hypotrophy.

Increased concentrations of placental lactogen in the blood are observed in multiple pregnancies, diabetes mellitus, and Rh incompatibility. Placental lactogen is also produced by trophoblastic tumors. The higher the degree of malignancy, the lower the ratio of placental lactogen and chorionic gonadotropin levels.

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