EXAM #1: ENDOCRINOLOGY OF OB/GYN Flashcards
What are the two main phases of the ovarian cycle? Which is first and which is second?
1) Follicular (phase 1)
2) Luteal (phase 2)
What happens during the follicular phase of the ovarian cycle?
1) Follicle development
2) Endometrial proliferation
What happens during the luteal phase of the ovarian cycle?
1) Formation of the corpus luteum
2) Endometrial differentiation
What hormone predominantes in the follicular phase of the ovarian cycle?
Estrogen
What hormone predominantes in the luteal phase of the ovarian cycle?
Progesterone
How is GnRH released? Where is GnRH released from?
GnRH is released in a pulsatile fashion from the hypothalamus
Overall, what is the concentration of LH and FSH during the ovarian cycle?
Low
How does the feedback of estrogen on the hypothalamus/anterior pituitary change throughout the ovarian cycle?
- Generally there is negative feedback
- Mid-cycle i.e. ovulation there is POSITIVE feedback
What synthesizes the inhibins?
Granulosa cells of the ovary
When is the concentration of Inhibin B the highest?
Follicular phase and just post ovulation
What hormone does Inhibin B exert negative feedback on?
FSH
When is the concentration of Inhibin A the highest?
Luteal phase
Describe how estradiol is produced during the follicular phase of the ovarian cycle.
1) Theca cells synthesize androstenedione in response to LH
2) Graulosa cells= FSH controls the conversion of androstenedione to estradiol
In the follicular phase, what do Theca cells synthesize?
Androstenedione
What controls the production of androstenedione from theca cells in the follicular phase of the ovarian cycle?
LH
After the formation of a mature/dominant follicle in the follicular phase of the ovarian cycle, what change in hormone levels correspond with follicular atresia of the non-dominant follicles?
- Decrease in FSH
- Increase in Inhibin B
What is the effect of estrogen on the endometrium?
Proliferation
What is the effect of progesterone on the endometrium?
Differentiation
At day 14, a surge in _____ causes ovulation?
LH and FSH
What is absolutely required for ovulation to occur?
Surge of LH
Why can basal body temperature (BBT) be used as an indirect marker of ovulation?
Progesterone causes an increase in basal body temperature
What is the corpus luteum?
Temporary endocrine gland in the ovary that secretes estradiol and progesterone
How does LH increase the synthesis of progesterone?
1) LH upregulates genes of progesterone synthesis
2) Increased cholesterol uptake for progesterone synthesis
How are the ovarian follicle and the corpus luteum related?
Follicle becomes the corpus luteum after ovulation
What hormone inhibits the HPG axis during the luteal phase? How does this negative feedback compare to the follicular phase?
- Inhibin A
- Negative feedback is more intense
What does the corpus luteum become once it has regressed?
Corpus albicans
What is “hatching” in implantation and formation of the placenta?
Breakdown of the zona pellucida
What is “apposition” in implantation and formation of the placenta?
Trophoblast contact with the endometrium in the uterus
What is “ adhesion” in implantation and formation of the placenta?
Integrin mediated attachment of the trophoblast (embryo) and decidua cells of the endometrium
What happens in “invasion” during implantation and formation of the placenta?
1) Trophoblast becomes cytotrophoblast and syncytiotrophoblast
2) Syncytiotrophoblasts send out protrusions that invade the endometrium
What happens after the syncytiotrophoblasts invade the endometrium?
1) Syncytiotrophoblasts invade maternal veins and arteries
2) Primary chorionic villi form
If fertilization occurs, what hormone is produced to maintain pregnancy?
hCG is produced by the syncitiotrophoblast cells of the placenta
What does hCG bind to? What does hCG maintain?
- Binds LH receptors
- Maintains the corpus luteum
After the first 8 weeks of pregnancy, what secretes progesterone and estrogen?
Syncitiotrophoblast cells of the placenta
What is hPL?
Human Placental Lactogen
What are the functions of hPL?
1) Fetal metabolism
2) Fetal growth and development
What secretes hPL?
Syncitiotrophoblast cells of the placenta
What aside from the hypothalamus secreted CRH? When is this secreted?
- Syncitiotrophoblasts and trophoblasts
- Dramatic increase prior to delivery
What is the key role of the androgens/ DHEA in pregnancy?
This is the substrate for estrogen synthesis
Where does DHEA come from?
1) Maternal adrenal gland
2) Fetal adrenal gland
3) Fetal liver
