Reproductive Endocrinology III Flashcards
(46 cards)
Name some key aspects about the endocrinology of pregnancy.
1) Functions of the placenta
2) Hormones of the placenta
3) Maternal nutrition and transfer of nutrients to the fetus
4) Control of the length of gestation (timing of parturition / birth)
The placenta…
Only appears during pregnancy, and it connects the maternal and fetal circulation.
The trophoblast is the ______ of the placenta.
fetal component
The decidua is the _______ of the placenta.
maternal component
Name the four characteristics of the placenta.
1) It is a respiratory, alimentary and excretory organ.
2) It is an endocrine organ: steroid and protein hormones are secreted into the maternal circulation.
3) It participates in the control of fetal endocrine function, growth and development.
4) It is a selective barrier that governs the interaction between the fetal and maternal compartments.
Hormones of the placenta are important for orchestrating…
the transfer of nutrients from the mother to the fetus (largely through effects on maternal energy balance)
Hormonal changes that occur in the mother are…
Adaptive; they affect maternal physiology and allow the mother to nurture the fetus.
Internal milieu during pregnancy is….
*Although…
mostly not growth promoting for maternal tissues
*(but some maternal organs do grow aka heart, thyroid, uterus, breasts, etc.)
Hormones changes in maternal environment promote…
nutrient-sparing for the developing fetus.
Why are hormones of the placenta important? (3 reasons)
1) Do the transfer of nutrients from the mother to the fetus, largely through effects on maternal energy balance.
2) Maintain the growth and functioning of the placenta
3) Directly influence (in some cases; e.g., sex steroids, thyroid hormones) the growth and development of the fetus.
Name the polypeptide hormones of the placenta (3).
- Chorionic Gonadotropin (human-hCG)
- Placental Lactogen: looks like PRL but is distinct
- Placental Growth Hormone
Name other chorionic peptide hormones and growth factors of the placenta.
- Peptides derived from POMC (ACTH, endorphins)
- CRH
- CRHBP
- GnRH (same as hypothalamic GnRH - may control release of hCG)
- TRH
- FGF
- EGF
- PDGF
- IGFs
*Think… which ones are growth factors? (the last…)
Placental growth hormone (GH) is different from pituitary GH by ____ amino acids out of ____.
13, 191
Which growth hormone production increases during pregnancy and which decreases?
Placental GH rises, pituitary GH drops.
Placental GH mobilizes maternal nutrients for fetal growth by inducing ___________. What does this also do?
Maternal insulin resistance; it leads to impaired maternal glucose utilization.
Human chorionic gonadotropin (hCG) is first detectable in blood…
*How often does its concentration double and what is its half-life?
24 hours after implantation.
*1.7-2 days, half-life is 24 hours.
What is the interesting fact about hCG in fetal blood circulation?
Only a very small % actually gets into the fetal blood, but it plays a VERY important role.
Human placental lactogen (hPL) is first detectable in blood…
*How does it’s concentration increase and what is its half-life?
4-5 weeks of gestation.
*Its concentration increases steadily through the end of gestation, it’s half-life is 15-30 minutes.
Placental lactogen may ____ maternal food intake during ____ & ____ by inducing ___________.
- increase
- early & mid-pregnancy
- central leptin resistance
Placental lactogen promotes ____________ and ___________.
*Why? (hint: diabetes mellitus)
- maternal pancreatic beta cell growth
- insulin production
*to defend against the development of gestational diabetes mellitus (this could occur in part due to the actions of placental GH)
The disappearance of IGFBP3 from maternal serum during human pregnancy leads to a…
*What enzyme degrades IGFBP3?
decrease in serum IGF-1.
*An enzyme in the kidney.
How does the placenta make steroid hormones?
*i.e. progesterone and estrogen
It converts them from cholesterol. It is a steroid-converting organ because it cannot make cholesterol like the gonads and the adrenal.
How do placenta (progesterone) and corpus luteum (17-hydroxyprogesterone) change during pregnancy.
17-hydroxyprogesterone peaks at the end of the first trimester (this is also when miscarriages are most common)
Progesterone will rise after 17-hydroxyprogesterone drops down, because it is being produced by the newly developed placenta.
During the second trimester estriol estradiol and estrone all rise in the maternal plasma. But how are these made?
(Hint: DHEA-S ~> Estradiol 17β
1) In placenta fetal adrenal DHEA-S is converted to DHEA by sulfatase.
2) DHEA -> androstenedione
3) Androstenedione -> testosterone
4) Testosterone -> estriol
5) Estriol -> estradiol 17β
