Endocrine: pregnancy
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- What are three functions of the placenta?
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1.Delivery of nutrients to the fetus
2.Removal of wastes from the fetus
3.Synth of steroid and peptide hormones - How is estrogen produced during the mentrual cycle?
- TST is synth by the theca cells and then converted to estrogen by the granulosa cells.
- What 2 hormones can stimulate and maintain the corpus luteum?
- LH (from the ant pituitary) and hCG (from the embryo)
- Describe the structure of hCG. What's its function?
- hCG is a a-b heterodimer glycoprotein similar to LH, FSH, and TSH. It binds LH receptors on the corpus luteum to maintain progesterone production.
- What role does progesterone play in early pregnancy?
- It is secreted by the corpus luteum and maintains the endometrium for implantation and development of the early embryo.
- The corpus luteum is important for progesterone production only until 10 weeks gestation. Where does the hormone come from after that?
- The placenta takes over synthesis and secretion of progesterone past 10 wks.
- What is hCS? Where is it secreted from? What are its functions?
- A peptide hormone synth and secreted by the placenta. It increases the energy available to the fetus by decreasing maternal glucose use, enhancing fat mobilization, and it weakly stim milk production.
- What are three functions of estrogen during pregnancy?
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1.Increases uterus size
2.Induces expression of oxytocin and progesterone receptors
3.Increases mass of breasts and adipose tissue - What are 3 functions of progesterone during pregnancy?
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1.Maintains implantation
2.Inhibits myometrial contractions
3.Local immunosuppression - What two things does the placenta lack for the synthesis of steroid hormones?
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1.Unable to synth cholesterol from acetate
2.Lacks enzymes for estradiol synth - The fetus is able to synth estrogen precursors but not the functional molecule. Why?
- This is probably a protective function that prevents the fetus from accumulating a daangerous amount of the hormone.
- What is the major precursor used by the placenta for estrogen synthesis? Where does it come from?
- DHEA-S, which is made in the fetal adrenal glands. DHEA-S is converted to DHEA and then to androgens and estrogens in the placenta.
- What anatomical adaptation allows the fetus to participate in the synthesis of estrogen?
- The fetal adrenal gland has a specialized fetal zone where DHEA-S is synthesized. DHEA-S can be used by the placenta, or converted to estriol by the fetus. The zone regresses before birth.
- During pregnancy the thyroid gland increases in size and activity. Why are no symptoms of hyperthyroidism seen?
- The liver increases synthesis of thyroid hormone binding protein.
- Describe the levels of FSH and LH during pregnancy.
- They are low due to supression by high levels of estrogen and progesterone.
- What happens to the anterior pituitary during pregnancy?
- It grows in size as lactotrophs hypertrophy and increase production of PRL.
- Pregnant women are often in a hyperglycemic state. How does this occur and what is its benefit?
- There is increased synthesis of anti-insulin hormones. This increases the glc gradient btwn mother and fetus and thus enhances delivery of glc to the fetus.
- What substance has been correlated with birth weight?
- IGF-II. Similar to IGF-I, but not under control of GH.
- What two things increase the risk of rickets in neonates?
- Feeding exclusively by breast, low exposure to sunlight.
- What hormone has been implicated in both postpartum depression and PMS?
- The acute drop in progesterone is thought to play a role in both of these.
- What is the "morning after" pill? Name three mechanisms by which it might work.
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Synthetic progesterone.
1.Inhibit ovulation
2.Change cervical mucus
3.Change endometrium to prevent implantation. - What is RU-486? How does it work?
- A synthetic progesterone antagonist that induces menstruation.