Question
Explain the role of hPL hormone in pregnancy and its physiological effects.
Solution
PrepMate
Human placental lactogen (hPL), also known as human chorionic somatomammotropin (hCS), is a polypeptide placental hormone whose structure and function are similar to those of human growth hormone (hGH). It plays a significant role in regulating maternal and fetal metabolism during pregnancy, as well as in promoting fetal growth and development.
Human placental lactogen (hPL), also known as human chorionic somatomammotropin (hCS), is a polypeptide placental hormone whose structure and function are similar to those of human growth hormone (hGH). It plays a significant role in regulating maternal and fetal metabolism during pregnancy, as well as in promoting fetal growth and development.
The role of hPL in pregnancy can be understood through its various physiological effects:
1. Modulation of Maternal Metabolism: hPL helps to ensure that adequate nutrients are available for the developing fetus. It does this by altering maternal metabolism. hPL reduces maternal insulin sensitivity, which leads to an increase in maternal blood glucose levels. This process is often referred to as 'diabetogenic effect' of hPL, ensuring that glucose is available for the fetus to use.
2. Lipolysis Stimulation: hPL stimulates lipolysis, which is the breakdown of maternal adipose tissue into free fatty acids. This provides an alternative energy source for the mother, sparing glucose for use by the fetus.
3. Breast Development: hPL also plays a role in preparing the breasts for lactation. It promotes the growth of mammary glands, which is essential for milk production post-delivery.
4. Regulation of Fetal Growth: hPL has growth-promoting activities. It contributes to the regulation of fetal growth by directly affecting the metabolism of the fetus and by modulating the maternal supply of nutrients.
5. Modulation of Immune Tolerance: hPL may play a role in modulating the maternal immune system to tolerate the fetus, which is genetically distinct from the mother.
The production of hPL begins early in pregnancy and is secreted by the syncytiotrophoblast cells of the placenta. The levels of hPL increase steadily until term, with the highest levels observed during the third trimester. This correlates with the period of most rapid fetal growth, underlining the importance of hPL in providing an optimal environment for fetal development.
In summary, hPL is a crucial hormone for pregnancy, with multiple roles in ensuring the growth and well-being of the fetus, as well as preparing the mother's body for childbirth and lactation. Its effects on maternal metabolism and fetal growth highlight the intricate balance of hormonal regulation necessary for a successful pregnancy.
The role of hPL in pregnancy can be understood through its various physiological effects:
1. Modulation of Maternal Metabolism: hPL helps to ensure that adequate nutrients are available for the developing fetus. It does this by altering maternal metabolism. hPL reduces maternal insulin sensitivity, which leads to an increase in maternal blood glucose levels. This process is often referred to as 'diabetogenic effect' of hPL, ensuring that glucose is available for the fetus to use.
2. Lipolysis Stimulation: hPL stimulates lipolysis, which is the breakdown of maternal adipose tissue into free fatty acids. This provides an alternative energy source for the mother, sparing glucose for use by the fetus.
3. Breast Development: hPL also plays a role in preparing the breasts for lactation. It promotes the growth of mammary glands, which is essential for milk production post-delivery.
4. Regulation of Fetal Growth: hPL has growth-promoting activities. It contributes to the regulation of fetal growth by directly affecting the metabolism of the fetus and by modulating the maternal supply of nutrients.
5. Modulation of Immune Tolerance: hPL may play a role in modulating the maternal immune system to tolerate the fetus, which is genetically distinct from the mother.
The production of hPL begins early in pregnancy and is secreted by the syncytiotrophoblast cells of the placenta. The levels of hPL increase steadily until term, with the highest levels observed during the third trimester. This correlates with the period of most rapid fetal growth, underlining the importance of hPL in providing an optimal environment for fetal development.
In summary, hPL is a crucial hormone for pregnancy, with multiple roles in ensuring the growth and well-being of the fetus, as well as preparing the mother's body for childbirth and lactation. Its effects on maternal metabolism and fetal growth highlight the intricate balance of hormonal regulation necessary for a successful pregnancy.
Hormones
Hormones and Receptors
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Hi. I'm glad you're back to continue our discussion of the endocrine system.
We were talking in our previous video about
lipid-derived hormones, lipid-soluble hormones,
and remember that many of them,
at least, were products of,
or similar to, cholesterol.
Cholesterol served as a basis for their continued biochemistry.
Steroid hormones though, must be insoluble in water.
So the question arises: How are they transported through the blood because,
if they're not soluble in water,
then they won't be soluble in blood?
The way that happens,
the way they move through the blood,
is that they become attached to a transport protein.
The transport protein is soluble in water, in the blood.
Therefore, the fat-soluble globule can move through the bloodstream,
and it can therefore also deposit the fat globule,
or the lipid globule,
on the surface of a plasma membrane,
and then it can diffuse through.
Notice here the receptor is inside the cell, in this case,
inside the nucleus, even of the receptor cell.
Let's see how this happens.
A consequence actually of this system is that
they remain in circulation considerably longer than peptide hormones.
I want to give you an idea of how quickly these things can
degrade or can stay inside the bloodstream.
Cortisol, which is,
of course, soluble in water,
"ol" means that it's an alcohol,
has a half-life of about 60-90 minutes.
What's a half-life?
The half-life is the time that elapses in which about 50 percent,
half, of this material disappears.
So in 60-90 minutes, cortisol is half-gone.
On the other hand, epinephrine,
so that's an amino acid-derived hormone,
has a half-life of approximately 1 minute.
Cortisol is the lipid, "ol",
that's an alcohol, but it is derived from a lipid,
has a much longer half-life than the amino acid-derived hormone which is water-soluble.
Let's look now at amino acid-derived hormones.
In particular, we'll put 2 amino acids,
tyrosine and tryptophan, which serve as basis for a number of different hormones.
You can see epinephrine is quite similar to tyrosine,
and melatonin is quite similar to tryptophan.
If you look at it, the difference between epinephrine and tyrosine really is very small,
and the difference between melatonin and tryptophan is quite small.
Look at the R groups over here.
But in any case, we also name these hormones based on what they come from,
just as we saw in the cholesterol-based hormones.
The chemical name will end in "ine" or sometimes in "in",
if they come from these amino acids.
Epinephrine and norepinephrine,
"ine" at the end, thyroxine,
"ine" at the end, or melatonin just "in",
each of these is derived from an amino acid.
In the case of peptide hormones,
we're talking about a polypeptide chain,
not just 1 amino acid because a polypeptide is a chain of amino acids,
and those include various hormones, for instance,
the antidiuretic hormone,
ADH, or oxytocin,
and also growth hormones,
or FSH, follicle stimulating hormone,
which is involved in ovulation in women.
Amino acid-derived polypeptide hormones are water-soluble.
Therefore, they can go through the bloodstream,
simply dissolved in the bloodstream,
and they cannot pass through plasma membranes.
They're not going to be soluble in plasma membranes,
and therefore the receptor for them is going to have to be on the target cell.
Thus, the receptor is going to have to be on
the target cell on the outside in the plasma membrane.
Then as we mentioned earlier,
there'll be a signal transduction pathway which will lead the signal into the nucleus.
This video discusses the differences between lipid-derived and amino acid-derived hormones, and how they are transported through the bloodstream. Lipid-derived hormones, such as cortisol, are insoluble in water and must be attached to a transport protein to move through the bloodstream. These hormones have a longer half-life than amino acid-derived hormones, such as epinephrine. Amino acid-derived hormones are water-soluble and can move through the bloodstream without a transport protein. However, they cannot pass through plasma membranes, so the receptor must be on the target cell on the outside of the plasma membrane.
- Lipid-derived hormones are insoluble in water and must be attached to a transport protein to move through the bloodstream
- Lipid-derived hormones have a longer half-life than amino acid-derived hormones
- Amino acid-derived hormones are water-soluble and can move through the bloodstream without a transport protein
- Amino acid-derived hormones cannot pass through plasma membranes, so the receptor must be on the target cell on the outside of the plasma membrane
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