Endocrinology of OBGYN Flashcards
what are the two phases of the ovarian cycle? when does each begin?
follicular - begins day 1
luteal - begins after ovulation
what are the features of the follicular phase
- what forms / develops
- what happens to the endometrium
- what follows?
- follicle development
- endometrial proliferation
- follicular phase is followed by ovulation
what are the features of the luteal phase?
- what forms / develops
- what happens to the endometrium
- what follows?
- corpus luteum forms
- endometrial differentiation
- followed by menses
when does FSH rise in the ovarian cycle?
early in follicular phase, and also at ovulation
what is the role of estrogen during the follicular phase on the anterior pituitary?
negative feedback
what is the role of estrogen during mid-cycle on the anterior pituitary?
36 hours of relatively high estrogen concentrations exert positive feedback at the level of the anterior pituitary
what is the role of estrogen (and progesterone) during the luteal phase on the anterior pituitary?
negative feedback
when does inhibin A rise? what is its role?
luteal phase
negative feedback
the inhibins are synthesized by what cells of the ovary?
granulosa cells
what is an important role of inhibin B
regulation of FSH
follicular phase is associated with what hormone?
estrogen
theca cells synthesize androstenedione in response to what hormone?
LH
where is androstenedione converted to estradiol? what regulates this process?
granulosa cells
FSH regulates this conversion
follicular phase has a role for what two hormones?
FSH and LH
early to mid follicular phase - what is estrogen doing?
applying negative feedback on HPG axis
why does estrogen continue to rise during the follicular phase despite negative feedback on LH and FSH?
presence of more theca cells, and more secretions from those theca cells
also increased sensitivity, so more steroid production
at day 14, what induces ovulation? what is absolutely required?
surge in LH and FSH
LH is absolutely required
what hormone is responsible for the rise in basal body temperature during ovulation?
progesterone
the corpus luteum forms from what cell types?
thecal granulosa fibroblast endothelial immune cells lipids
when does the corpus luteum reach maturity?
7-8 days following ovulation
what is the change in the regulation from the follicular phse to the luteal phase?
LH becomes key regulator in the luteal phase - theca cells become more responsive to LH
what is the key difference in granulosa cells during the luteal phase?
- LH now regulates
- progesterone synthesis is now occurring
- increased in uptake of cholesterol
during the luteal phase, what hormone regulated the differentiation and secretory development of uterine endometrium?
progesterone
what are the key endometrial changes during the luteal phase?
- increased complexity of vascular and glandular structures
- accumulation of substances in glands
- deposition of lipids and glycogen in stromal cells
- increased blood supply
what allows for the ovarian cycle to reset?
- regression of corpus luteum - decline in steroid cynthesis
- decrease in negative feedback on anteior pituitary (concentrations of LH and FSH rise)
what are the steps of implantation?
- hatching
- apposition
- adhesion
- invasion
what constitutes ‘hatching’ during implantation and formation of the palcenta?
breakdown of zona pellucida
what constitutes ‘apposition’ during implantation and formation of the placenta?
trophoblastic cells of the blastocyst make contact with endometrium
what constitutes ‘adhesion’ during implantation and formation of the placenta? what mediates this process?
integrin mediated attachment between trophoblast and stromal cells (decidual cells) of the endometrium
what constitutes ‘invasion’ during implantation and formation of the placenta?
- trophoblast differentiates into cytotrophoblast and syncitiotrophoblast
- syncitiotrophoblasts send out protrusions and invade endometerium
what are the steps of placenta formation?
- invading syncitiotrophoblast breaks through maternal veins and arteries
- allows for pools of maternal blood to interface with syncytiotrophoblasts
- primary chorionic villi form
- within villi, capillaries form
what are the components of the fetal placenta?
- syncytiotrophoblasts
- cytotrophoblasts
- mesenchyme
- fetal blood vessels
what is contained in the intervillous space?
blood trapped between fetal villous and maternal endometrium
what are the components of the maternal placenta?
- decidual cells
- maternal arteries and veins
what happens to the corpus luteum upon implantation?
- placental derived hCG stimulates ovarian steroidogenesis
- secretes relaxin to inhibit myometrial contractions
after week 8 following implantation, maintenance of pregnancy is dependent upon what hormones? what are their roles?
progesterone - suppress uterine contractions, inhibit PG production, impact immune response
estrogen - stimulate uterine growth, thicken vaginal epithelium, growth, and development of mammary epithelium
what are the physiological roles of hCG? where does it bind?
- bind LH receptors
- maintain corpus luteum
- maintain ovarian steroid production needed for first 7-8 weeks of gestation
where is hCG produced? when is it secreted? when does it peak?
- syncytiotrophoblast (fetal placenta-derived)
- secreted around week 6 of pregnancy
- increases throughout pregnancy
what are the physiological roles of human placental lactogen (hPL)?
- fetal metabolism
- fetal growth and development
- stimulates production of IGF, insulin, adrenocortical hormones, surfactant
where is hPL produced? when is it secreted? when does it peak?
- syncytiotrophoblast
- secreted around week 6 of pregnancy
- increases throughout pregnancy
what are the physiological roles of CRH?
- onset of labor
- production of PGs
- maintain blood flow in placenta
where is CRH produced? when does it peak?
- syncytiotrophoblast and trophoblast
- increases throughout pregnancy and peaks during labor
what are the physiological roles of progesterone and 17-hydroxyprogesterone?
- inhibit PG production
- suppress uterine contractions
- modulate immune response
where is progesterone produced during pregnancy? what is required for its production?
- first 8 weeks, produced by corpus luteum under control of hCG
- after 8 weeks, produced by syncytiorophoblast
- requires use of maternal LDL
what are the physiological roles of DHEA?
substrates for estrogen synthesis
where is DHEA produced?
- maternal adrenal gland
- fetal adrenal gland
- fetal liver
