Regulation of the Female Reproductive Cycle Flashcards
What stimulates GnRH release in the brain?
NE
What inhibits GnRH release in the brain?
DOPA
What are the cellular actions of GnRH?
- GnRH acts via a GPCR and increases Ca which causes FSH/LH release
- GnRH action via DAG will increase FSH and LH synthesis
What is the function of follistatin?
It binds activin which will reduce its concentration and result in the inhibition of of the pituitary for GnRH
What is the effect of the drug Clomiphene?
It is a fertility drug that acts as an E2 receptor antagonist as with decreased E2 binding there will be less negative feedback and the GnRH pulse will increase as a result
What occurs in the follicular phase?
Time of follicle growth that occurs from menses onto ovulation
What is the hormone control in the follicular phase?
GnRH ->
FSH/LH release ->
E2 release ->
Follicle development
What is the feedback found in the follicular phase?
E2 and inhibit have negative feedback on the hypothalamus and the pituitary that will keep GnRH volume down
What makes Inhibin A?
Corpus Luteum
What makes Inhibin B?
Dominant Follicle
What occurs in the ovulatory phase?
It occurs over 1-3 days and the final oocyte maturation and release occurs
What is the hormonal control in the ovulatory phase?
E2 levels reach a threshold and positive feedback will occur that causes an LH surge leading into ovulation
What is the feedback found in the ovulatory phase?
Follicle rupture causes a decrease in E2 and loss of E2 positive feedback that occurs up to ovulation. This leads to a decrease in LH.
What happens to the follicle after ovulation?
It reorganizes into the corpus luteum
What occurs in the luteal phase?
Corpus luteum forms and hormones that promote implantation are released
What hormones are released in the luteal phase?
The corpus luteum is dominant and so E2 and progesterone are released
What is the feedback in the luteal phase?
Progesterone has strong negative feedback and E2 becomes inhibitory leading to decreased GnRH, LH and FSH
What happens to the corpus luteum at the end of the luteal phase?
It will degrade without LH due to the decreasing LH unless it is rescued by hCG
What is the process occurring with menses?
E2/progesterone are low after the luteal phase with the loss of the corpus luteum and FSH increases without negative feedback leading to endometrial sloughing
What is required for the development of primordial follicles into primary follicles?
FSH/LH and appropriate E2 levels
How are secondary follicles developed from primary follicles?
To make this follicle type, the theca cells proliferate and develop LH receptors.
Granulosa cells acquire receptors for FSH, androgens and estrogens.
What is the inhibitory function of the dominant follicle?
Inhibits growth of other follicles, even those in the other ovary
What are the other functions of the dominant follicle?
Alter cervical mucus to enhance sperm transport
Change fallopian tubes to enhance sperm transport
What is the Two Compartment Theory of Graafian Follicle Steroidogenesis?
The theca and granulosa cells cooperate
What is the role of the granulosa cells in the two compartment theory?
They have high aromatase with FSH stimulation and also produce progesterone and pregnenolone.
They cannot convert 21-C precursors into androgens very well
What is the role of theca cells in the two compartment theory?
With LH stimulation they produce androgens and transport them to the granulosa
What is the vascularization of the theca/granulosa cells?
The theca is well vascularized and has better access to circulating cholesterol
What is the overall pathway of the Two Compartment Theory?
The theca takes cholesterol from the circulation and forms androgens. The androgens are then passed to the granulosa cells which are rich in aromatase and convert them into E2
What are the phases of menstruation as described in terms of endometrial functions?
Proliferative
Secretory
Menstrual
What occurs in the proliferative phase and what is the dominant hormone?
E2 is dominant. In the mid to late follicular phase the endothelium thickens with spiral artery development and increased progesterone and estrogen receptors.
What occurs in the secretory phase and what is the dominant hormone?
Progesterone is dominant. Occurs during ovulation to late luteal phase and it shows increased vascularization and mucus secretion that is rich in carbohydrates.
What occurs in the menstrual phase and what is the dominant hormone?
E2 and Progesterone are both low. Restriction of the spiral arteries leads to ischemia and necrosis with the rupture of blood vessels and infiltration of leukocytes.
What is Spinnbarkeit and what is it indicative of?
It is stretchable mucus that indicates ovulation
What is menopause?
It is the loss of negative feedback from E2 and inhibit that causes an increase in FSH/LH with FSH>LH which is different from the normal ratios.
What are some of the consequences of menopause?
Osteoporosis
CV Disease
Decreased breast mass
Hot flashes
What was found to be the effects of hormone replacement therapy in menopausal women?
Only shown to be beneficial for osteoporosis and most beneficial if used immediately at menopause rather than some time after.
