Lecture 26 Flashcards
(21 cards)
What is the whole purpose of hormone secretion during pregnancy?
- maintain the early stage in pregnancy
- modification of the maternal metabolism
- prepare for the actual birthing event and lactation
Why is human chorionic gonadotropin (hCG) important during pregnancy? Explain how this ties into the corpus luteum. When do hCG levels decrease? Why?
hCG is important for the maintenance of the pregnancy, formation of the placenta, and everything else to do with the early stages of pregnancy. After ovulation, this causes circulating LH leels to be much higher, leading to the corpus luteum being stimulated to produce and secrete progesterone and estrogen as a result. These increasing levels of progesterone and estrogen act to suppress anterior pituitary secretion of LH. This will lead to decreasing concentrations of LH and thus the dying off of the corpus luteum into the corpus albicans in the event that fertilization doesn’t occur.
Assuming it does occur:
- When the zygote implants, the cells that surround the growing embryo are going to be responsible for the production of hCG, which acts of the corpus luteum to keep it around longer. the hCG stimulates the corpus luteum to produce progesterone and estrogen, allowing for the maintenance and development of the pregnancy. When the placenta ends up getting formed, hCG secretion will end up decreasing, so the fetal-placental unit takes over the role of progesterone and estrogen production. However, the placenta will still be responsible for the production of hCG, since hCG helps support the growing fetus.
When is the beta subunit of hCG detectable in serum (after conception?) What about in urine/ Is there a correlation between hCG concentrations and the success of pregnancy?
It’s detectable in blood about 8 days following conception. In urine, it is detectable 2-4 days after that.
There is a correlation between higher amounts of hCG that is produced and the success of the pregnancy. Levels of hCG during pregnancy depends on age. After 35-40 years old, you become a high risk pregnancy.
What hormones are produced by the placenta and/or embryo? What are their purposes?
- human placental lactogen: effects on metabolism, responsible for decreasing glucose uptake, decreasing insulin sensitivity, increasing lipolysis
- gonadotropin releasing hormone (embryo): helps support the early portion of pregnancy. helps with implantation and helps begin the hCG secretion in the 1st and 2nd trimesters
- corticotropin releasing hormone (placenta): involved in timing of childbirth. will stimulate prostaglandin synthesis, uterine contractions, fetal steroidogenesis by increasing ACTH
Why is there a correlation between hormones and high incidence of gestational diabetes? What can occur as a result of developing gestational diabetes?
Human placental lactogen
Since human placental lactogen decreases insulin sensitivity and decreases muscle/tissue uptake of glucose, this causes higher levels of maternal blood glucose.
If these hormones go into overdrive, this could end up leading to the development of gestational diabetes. If that occurs and blood sugar levels aren’t regulated, this could lead to a high risk pregnancy and the development of a huge baby.
Development of a huge baby is not good because it can cause more damage as a result of birthing. In addition, larger babies end up outgrowing the placenta.
During pregnancy, estrogen and progesterone are the key hormones for what? What precursor is used for estrogen formation?
They are the key hormones for maintenance/development of pregnancy, delivery, and lactation. The precursors used for estrogen formation is testosterone.
What hormones do the maternal adrenals produce for the growing fetus? What does the placenta produce? What about the fetal adrenals and the fetal liver? Where do these hormones go after they are produced?
The hormones are dehydroepiandrosterone (DHEA) and androgen from cholesterol (through PKA/StAR pathway) such that DHEA can go from the maternal circulation to the placenta to lead to the production of androstenedione, which is used for the production of estrogen. The mothers cholesterol is able to circulate to the placenta to lead to the production of progesterone.
The fetal adrenals are also responsible for the production of DHEA, such that this can be sent to the placenta for the production of estrogen.
The mothers cholesterol is able to circulate to the placenta to lead to the production of progesterone.
The fetal adrenals are also responsible for the production of DHEA, such that this can be sent to the placenta for the production of estrogen.
The fetal liver is responsible for the production of DHEA, such that this can be sent to the placenta for the production of estrogen.
The hormones produced are sent into maternal circulation.
During pregnancy, what are the roles of estrogen and progesterone?
Progesterone:
- responsible for maintenance of the placenta, making sure it works properly
- decrease uterine contractions
- helps with the growth and the development of the mammary glands
Estrogen:
- responsible for maintaining the endometrium in the early weeks of pregnancy, which is needed so that the egg can implant properly to get enough nutrients
- increases uterine contractions
- helps with the growth and development of the mammary glands
How high are concentrations of E3 (estriol) in non-pregnant women? What do levels of E3 act as a marker for?
E3 is usually very low in non-pregnant women.
It’s used as a marker for fetal health
Before parturition, what hormone acts to keep the uterus in a quiet state? What hormone dominates at the onset of parturition, and what does this cause?
Before parturition, progesterone is going to contribute to maintain the uterus in a relaxed state and keep the cervix rigid. During pregnancy, the cervix will be sealed with a mucus plug and will be hard and thick, closing off the uterus from the outside world and acting in prevent infection. This is important because we don’t want childbirth until the baby is ready. Once labor starts, estrogen is going to dominate. This is where you have an increase in uterine contractions and thinning out of the cervix. The uterine contractions that occur are important for pushing the baby down through the birth canal.
Why is the timing of parturition important?
If birth occurs too early, this could compromise the infants health. If it’s too late, the uterine environment becomes too hostile to the fetus. If the pregnancy is late, the placenta will not be able to supply enough sugar, oxygen, or nutrients for the baby.
Why is early parturition bad? What happens in the event that someone goes into labor much sooner than expected?
The last things that a fetus develops is its lungs. If you end up going into labor too soon, doctors will try to prevent you form giving birth. In the event that you are at risk, doctors give the mother corticosteroids so that the lungs can develop more quickly so that they are ready to breath the outside air when they are born.
Once labor starts, it’s always characterized by what? Explain specifically what hormones experience this during labor and what this leads to.
It’s characterized by positive feedback loops.
Once the pregnancy starts, it keeps getting much worse/intense until the baby is birthed.
CRH and cortisol have positive feedback loops with each other. This will lead to more prostaglandin synthesis, which has a positive feedback loop with CRH as well. CRH also leads to more estrogen formation and more prostaglandin synthesis. The prostaglandins and estrogen synthesized will act to cause cervical ripening and increase uterine contractions until the baby comes out.
What does the hormone relaxin do during labor? How long does this hormone stay after pregnancy, and why can this be a bad thing?
Relaxin is important for making your joints more relaxed. The baby has to pass through the pelvic bones, so the joint in the pelvis need to be loosened up and spread, ensuring that there is some give in the bones for when the baby comes out. Relaxin stays around after pregnancy for a women at risk for injury since their joints are loose.
What role does oxytocin and prostaglandins serve during pregnancy?
Prostaglandins and oxytocin are involved in delivery (stimulates uterine contractions to induce labor.
In the event that labor needs to be induced early, or in the event of a late pregnancy, doctors will administer a synthetic form of oxytocin which will help initiate uterine contractions so that labor can be induced.
What is the role of cortisol produced by the fetal adrenals?
Cortisol from the fetal adrenals stimulates prostaglandin synthesis in the placental membranes. Cortisol also stimulates CRH synthesis in the placental membranes, thus allowing for more cortisol and prostaglandin synthesis. Cortisol from the fetal adrenals is also required for lung development. If you do not have the ability to wait until 40 weeks when you are full term, doctors will give you corticosteroids which will help with lung development because the lungs are one of the last things to develop.
The fetal adrenals are responsible for the production of DHEA. What is this utilized for, especially for/during parturition?
The fetal adrenals are responsible for the production of DHEA which is utilized for the production of estrogen synthesis in the placenta. The E2 which is produced especially during parturition is going to be responsible for directly stimulating uterine contractions. The E2 will also increase prostaglandin synthesis (responsible for stimulating uterine contractions)
What happens to the amount of oxytocin secreted and uterine oxytocin receptors produced as labor progresses?
As labor progresses, secretion of oxytocin and the amount of uterine oxytocin receptors increases. As a result, there will be more receptors which are able to bind oxytocin as its levels increase, thus stimulating more contractions. The contractions will stimulate more oxytocin to be produced, which further increase the amount of contractions.
Explain what hormones are produced which allow for fetal lung development as well as stimulation of contraction during parturition.
In the maternal hypothalamus, CRH is released such that it is sent to the anterior pituitary, where it stimulates corticotropes to produce and secrete adrenocorticotropic hormone -> ACTH sent to the fetal adrenals to stimulate -> produce dehydroepiandrosterone (DHEA) and cortisol
Cortisol production in the fetal adrenals is important because it helps lead to fetal lung development (essential for breathing) Cortisol production in the fetal adrenals leads to the synthesis of prostaglandins in the placenta. DHEA from the fetal adrenals can be sent to the placenta where estrogen can be produced. In the placenta, estrogen stimulates the production of prostaglandins. Both cortisol and DHEA synthesis can be stimulated in the fetal adrenals as a result of placental production of CRH. As a result of fetal adrenal cortisol production, this allows for the production of both the surfactant protein B for lunch development as well as prostaglandin synthesis. DHEA production and placental CRH stimulates estrogen production in the placenta as well.
The estrogen and prostaglandins that are produced in the placenta is able to stimulate uterine contractions during labor, leading to birth of the baby.
Besides estrogen, what other hormone leads to cervical ripening?
Relaxin
What hormone is responsible for the inhibition uterine contractions and cervical ripening?
Progesterone: inhibitor for the production of CRH and prostaglandins
