FSH acts where in the ovary?
Granulosa cells
**Inhibin and Estrogen
LH acts where in the ovary?
Theca cells
**androgens –> travel to granulosa cells to become estrogen
Estrogen has negative feedback on?
anterior pituitary AND hypothalamus
Inhibin has negative feedback on?
anterior pituitary ONLY
**primarily FSH
FSH role in ovary:
follicle development
LH receptor synthesis
What happens to estrogens negative feedback close to ovulation?
flips to positive feedback causing “LH surge”
FSH still suppressed by inhibin
**slide 11
LH role in ovary:
Critical for inducing ovulation
-ovulation required for formation of corpus luteum
Gonadotropin secreted by placenta:
What does it do?
hCG – human chorionic gonadotropin
1st trimester: maintains corpus luteum which keep progesterone (and estrogen) levels high to maintain pregnancy
stimulates LH receptor
Which two gonadotropins share a receptor?
LH and hCG
Progesterone comes from which cells?
thecal – LH and/or hCG mediated
**along with androgens
**progesterone also formed in luteal cells
What enzyme makes estrogens from androgens?
Aromatase
Main estrogen type:
17B estradiol
Estrogen receptor that mediates the HypPitOvar axis:
ERalpha
Look at slide 21…
weird feedback changes during ovulation
Difference between follicular phase and luteal phase:
follicular is before ovulation, luteal is after
high estrogen the whole time
higher progesterone in luteal
Estrogen effect on uterus during follicular phase?
promotes uterine growth (proliferative phase)
Progesterone effects on uterus during luteal phase?
maintains a high level of metabolism (secretory phase)
What is the chorion?
the placenta
Used to detect pregnancy:
Urinary hCG
When does uterine dependence on ovarian steroids switch to placenta steroids?
end of first trimester
Which steroid is dominant during most of pregnancy:
Progesterone
What are progesterones roles during most of pregnancy?
- decreases adrenergic receptors
- inhibits oxytocin receptor synthesis
- inhibits estrogen receptor synthesis
- promotes storage of PG synthesizing enzymes
When does estrogen become the dominant hormone of pregnancy?
just prior to birth (Parturition)
Estradiol roles during parturition:
- increases oxytocin receptors
- promotes uterine contractility
- cervical “ripening”
- Increases local prostaglandin release from placenta causing myometrial contractions
Prostaglandin roles in ovulation and pregnancy:
- rupture of Graafian follicle at ovulation
- contraction of myometrium during menstruation - mild Braxton Hicks contractions during pregnancy
- strong uterine contractions during parturition
**PG’s produced in placenta
Oxytocin role during parturition:
- induces smooth muscle contraction
**positive feedback with hypothalamus
What two things induce oxytocin release during parturition?
- mechanical stimulation of cervix
2. forceful uterine contractions
good summary slide on…
slide 35
What happens if placenta is not totally removed after delivery with regards to lactation:
progesterone is still inhibiting milk secretion
Galactopoiesis (milk PRODUCTION) controlled by:
prolactin
Milk ejection controlled by:
oxytocin
Lactation pathways on slide….
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