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„Hormonal changes during pregnancy” (Human chorionic gonadotrophin…
„Hormonal changes during pregnancy”
after ovulation: ruptured ovarian follicle -> corpus luteum
Corpus luteum – source of progesterone
II phase of menstrual cycle:
peak of secretion: about 8 days after peak of LH secretion
production: 10-40 mg/day
degeneration: 9-11 days after ovulation (artretic corpus luteum)
Pregnancy:
hCG (produced by trophoblast) „protects” corpus luteum from atresia, which results in maintaining progesterone synthesis.
progesterone synthesis:
till 7 weeks of pregnancy - only corpus luteum
7-10 weeks of pregnancy – transient period
after 10 weeks of pregnancy – mainly placenta (syncytiotrophoblast)
Progesterone
placental synthesis:
precursor: maternal LDL-fraction cholesterol
regulation: hcg and estradiol
additional synthesis: decidua and fetal membranes
metabolism: liver (90%), kidneys, muscles
function:
1.modulation of function of immune system
lymphocyte Th2 dominance and NK cells function, decreases endometrial lymphocytes T activity, suppresses „graft rejection”, regulate immunoglobulins synthesis, decreases amount of free radicals, decreases amount of proinflammatory cytokines
2.relaxation of myometrium and inhibition of uterine contractions „progesterone block”
3.substrate for fetal steroids hormones synthesis
4.lactation preparation, increases body temperature of pregnant
5.prevention of miscarriages and preterm births
Estrogens
synthesis:
corpus luteum – theory of „two cells”
(androgen synthesis in small lutein cells, and their aromatization to estrogens in big lutein cells)
pregnancy = hyperestrogenemia
at the beginning of pregnancy their function remains unknown
estriol is the main estrogen during pregnancy
other estrogens: estrone, estradiol, estetrol
function:
1.regulation of progesterone level
2 preparation of mammary glands to produce milk (with PRG, PRL, HPL)
3.cause uterine hypertrophy and increase blood flow through uterus
4 influence on hemostasis
5.cause insulin-resistance
6.stimulate synthesis of prolactin
7.stimulate synthesis of angiotensinogen
8.regulate function of fetal adrenal cortex
9.increase secretion of maternal melanocyte-stimulating hormone (MSH) – darken skin
Human chorionic gonadotrophin
synthesis: embryo, syncytiotrophoblast (placenta)
regulation: sexual steroids, cytokines, growth factor, GnRH
forms: regular hCG, hiperglycosylated hCG and free beta hiperglycosylated hCG
function:
regular hCG – development of placenta, stimulate fetal testes for testosteron synthesis,
hiperglycosylated hCG – produced by extrauterine invasive trophoblast (choriocarcinoma and carcinomas composed of embryonal cells)
hiperglycosylated beta hCG – neoplasms not connected with pregnancy
monitoring of concentration – blood and urine – free beta hCG (diagnostics of pregnancy)
diagnostics:
detectable 6-12 days after ovulation
8.-10. weeks of pregnancy – the highest levels 100000
from 20. week of pregnancy – constant level (10.000-20.000 jm/l)
diagnostic significance:
verification of gestational age
diagnostics of: ectopic pregnancy, molar pregnancy, multiple pregnancy, missed abortion, chromosomal abnormalities ( PAPP-A test)
Human placental lactogen (hPL)
produced and secreted by placenta (syncytiotrophoblast)
the structure of hPL is similar to PRL and GH
detectable from 5. week of pregnancy
concentration increases till the end of pregnancy (25 ug/ml)
function:
increases secretion of insulin
stimulation of lipolysis , inhibition gluconeogenesis
induction of catabolic processes intensifies transport of nutritious substances to fetus
Oxytocin
concentration (from placenta, fetal membranes, decidua) is 5 times higher then from pituitary gland
during pregnancy concentration increases
for regulation of uterine contractivity and secretion of milk
Relaxin
secreted by corpus luteum, placenta, fetal membranes, decidua
maximum concentration 8-12 weeks of pregnancy
causes ripening of uterine cervix tissue
increases concentration of cytokines
causes relaxation of myometrium (in early pregnancy)
Pituitary gland
enlargment of 120-140% during pregnancy
decreased concentration of FSH, LH (in 2. trymester – not detectable values)
decreased sensitivity to GnRH stimulation
estradiol, progesterone and inhibins (high concentration) suppress secretion of FSH, LH
prolactin:
10 x increase of prolactin concentration (caused mainly by estradiol)
synthesis: pituitary gland
function: preparation of mammary glands to lactation
TSH:
decreased between 9. and 13. weeks of pregnancy
biochemical similarity between TSH and hCG (hCG has thyrotropin activity) -> therefore increased concentration of hCG may caused „pseudo-hyperthyroidism” in early pregnancy
Hypothalamus
concentration of all hormones secreted by hypothalamus (in blood serum of pregnant) increases during pregnancy due to placental synthesis