B8.004 Female Endocrinology Flashcards
(69 cards)
1
Q
what part of the hypothalamus secretes GnRH
A
median eminence
2
Q
role of GnRH
A
gonadotropin releasing hormone
10 AAs
stimulates LH and FSH release from anterior pituitary
3
Q
role of FSH in ovary
A
follicle stimulating hormone
stimulates growth of follicles and estrogen synthesis and secretion
4
Q
role of LH in ovary
A
stimulates ovulation of mature follicle and formation of corpus luteum; stimulates estrogen and progesterone synthesis and secretion by corpus luteum
5
Q
regulation of GnRH
A
kisspeptin protein plays a role
receptor = GPR54
mutations can cause hypogonadotropic hypogonadism which leads to infertility
6
Q
2 types of kisspeptin expressing neurons
A
arcuate
AVPV
act via GPR54 on GnRH neurons
7
Q
what are gonadotrophs
A
cells in the anterior pituitary that produce LH and FSH
3-5% of cells, but contribute a lot to function
8
Q
function of GnRH neurons in HP axis
A
neurons release hormones into the median eminence that regulate anterior pituitary function
9
Q
discuss the portal system in the anterior pituitary
A
portal vein connects median eminence to anterior pituitary capillary bed allows for: low volume of hormones to be secreted high concentration pulsatile release rhythmic release
10
Q
life cycle of a follicle
A
primordial follicle vesicular follicle mature follicle (w antrum) ovulation/ corpus hemorrhagicum young corpus luteum mature corpus luteum regressing corpus luteum **a significant # of follicles go through atrophy rather than ovulating
11
Q
where does LH act in the ovary
A
thecal cells (antral follicles) granulosa cells (preovulatory follicles) luteal cells
12
Q
where does FSH act in the ovary
A
granulosa cells (follicles)
13
Q
types of estrogens
A
estradiol 17B (E2) most potent
estrone (E1) 10% potency
estriol (E3) 1% potency
14
Q
functions of estrogens
A
- stimulate secondary sex characteristics of female
- prepare uterus for sperm transport
- increase vascular permeability and tissue edema
- stimulate growth and activity of mammary glands and endometrium
- prepare endometrium for progestagen action
- mildly anabolic; stimulates calcification
- active during pregnancy
- regulate behavior and secretion of gonadotropins
15
Q
types of progestagens
A
progesterone (P4)
17a-OHP 40-70% potency
16
Q
functions of progestagens
A
- prepare uterus to receive conceptus
- maintain uterus during pregnancy
- stimulate growth of mammary glands, but suppress secretion of milk
- general mild catabolic effect
- regulate secretion of gonadotropins
17
Q
types of androgens
A
DHT (most potent)
T 50% potency
androstenedione 8% potency
DHEA 4% potency
18
Q
functions of androgens in women
A
- induce body hair
- influence sexual behavior
- promote protein anabolism, somatic growth and ossification
- regulate secretion of gonadotropins
19
Q
significant source of androgens in females
A
adrenal cortex
20
Q
estrogen and progesterone receptor types
A
function as transcription factors
21
Q
ERa vs ERb
A
ERa slightly longer distribution of specific estrogen receptors with certain organs CNS: a and b cardio: a and b lung: b GI: b GU tract: a and b bone: a and b liver: a breast: a and b
22
Q
what are activin and inhibin
A
members of TGFB superfamily
23
Q
activins function
A
produced by granulosa cells and pituitary folliculostellate cells
stimulate FSH transcription
24
Q
inhibins function
A
produced by granulosa cells
inhibit FSH transcription
25
follistatins function
produced by granulosa cells and pituitary folliculostellate cells
bind to and antagonize activins to prevent their action within gonadotrophs
26
estrogen functions in the HP axis
negative feedback
positive feedback
stimulates prolactin behavior
27
progesterone functions in the HP axis
negative feedback
28
androgens functions in the HP axis
behavior
| negative feedback
29
inhibin functions in the HP axis
decreases FSH
30
activin functions in the HP axis
stimulates FSH
31
follistain functions in the HP axis
indirectly decrease FSH
32
function of estrogen in the uterus
proliferation
| myometrium
33
function of progesterone in the uterus
development of glands and vasculature
myometrium
decidua cells
34
function of estrogen in the mammary gland
duct growth
fat deposition
inhibits milk synthesis
35
function of progesterone in the mammary glands
growth of the alveolar epithelium
| inhibits milk synthesis
36
other sites of estrogen action
vagina/cervix
liver
water retention
anabolic
37
other sites of progesterone action
vagina/cervix
| catabolic
38
primary functions of ovaries
1. folliculogenesis - oocyte maturation
| 2. hormone synthesis/secretion
39
structural changes that take place as follicle matures
grow larger with FSH and LH regulation
granulosa cells proliferate until multiple layers are present, eventually some die and the antrum (follicular fluid space) forms
thecal cells surround the follicle; initially one later (externa) but eventually and interna layer develops
40
layers of mature follicle from inside to outside
```
fully grown oocyte
zona pellucida
corona radiata
antrum
granulosa cells (multiple layers)
basement membrane
theca interna
theca externa
```
41
steroidogenesis within the ovary
cholesterol is starting point of steroid hormones
enzyme 3BHSD makes P4 from cholesterol
enzyme aromatase makes E2 from T
42
what happens with hormonal control as the follicle grows?
initially, large wave of multiple follicles growing
follicle needs FSH to grow
EVENTUALLY one follicle will reach a critical size at which point it becomes more FSH independent
granulosa cells in this follicle start producing more inhibin and estradiol to inhibit FSH secretion and prevent other follicles from growing larger
ONLY ONE FOLLICLE REMAINS
43
2 cell theory: theca cells
LH receptors present
-can be induced by LH or IGF1
convert cholesterol to T and intermediates (pregnenolone, 17OH pregnenolone, DHEA, androstenedione)
androstenedione and T then transported into granulosa cells for further conversion
**produces substrates for hormone production**
44
2 cell theory: granulosa cells
FSH receptors present
take androstenedione and T from theca cells and convert them to estrogens
during follicle growth, ratio of theca: granulosa favors granulosa cells
45
structures of LH and FSH receptors
g protein coupled
46
2 subtypes of graulosa cells
mural: outer layer
cumulus: surround oocyte, in direct communication
47
E2 secretion during the menstrual cycle
days 0-14: consistent rise
day 14: sudden drop with ovulation
days 14-28: flat line at intermediate level
**dominant in follicular phase**
48
P4 secretion during the menstrual cycle
```
days 0-14: low
day 14: spike
days 14-22: sharp rise
days 22-24: flat line
days 24-28: fall back to low levels
**dominant in luteal phase**
```
49
levels of feedback within the HPG axis
1. hypothalamic neurons (kisspeptin)
2. GnRH neurons at median eminence
3. gonadotropes in anterior pituitary
50
regulation of GnRH by hormone action at higher order neurons
negative feedback by estrogen on arcuate kisspeptin neurons
| positive feedback by estrogen on AVPV kisspeptin neurons once a threshold is reached
51
feedback loops during follicular phase
within ovary: granulosa cell mitosis, FSHR expression, and inhibin secretion
estrogen provides negative feedback at both hypothalamus and gonadotrophs
FSH dominant over LH
52
feedback loops during late follicular phase/ gonadotropin surge
estrogen provides POSITIVE feedback at hypothalamus and gonadotropes
-increased GnRH secretion
-increased GnRH-R number (more sensitive)
gonadotropes produce LH predominantly over FSH
53
result of LH surge in the ovary
increased granulosa cell LH-R
proteolytic factors allow breakdown of membrane surrounding follicle
meiotic block is removed
54
changes in granulosa cells at the luteal phase
acquire LH receptors, start to resemble theca cells more
| differentiation, reorganization, and altered gene expression
55
steroidogenesis within the ovary during the luteal phase
P4 predominantly produced
| estradiol at low levels
56
effects of progesterone secretion on HPG axis
negative feedback at levels of hypothalamus and gonadotropes
57
GnRH release pattern during luteal phase
higher amplitude
lower frequency
P4>E2
58
GnRH release pattern during follicular phase
lower amplitude
higher frequency
P4 declines, E2 rises
59
GnRH release pattern during gonadotropin surge
same amplitude as follicular phase
higher frequency (interpulse intervals don't allow for complete clearance)
high levels of E2
60
characterize the uterus during the follicular phase
1. proliferation
2. expression of P4-R
3. contractions
4. cervix changes
61
characterize the uterus during the luteal phase
1. gland development
2. uterine secretions
3. uterine vasculature
4. quiescence
62
adrenarche
adrenal androgen production prior to puberty
| secondary sex characteristics
63
FSH and LH levels during lifetime
peaks during 2nd trimester of fetal life, prior to 6 months of infancy, and rises again after menopause
remains relative low during childhood
slight rise during puberty
cyclic rising and falling during reproductive years
64
gonadotropin secretion during childhood
GnRH neurons primarily inhibited via GABA
65
gonadotropin secretion during puberty/adolescence
```
more excitatory neurotransmission acting on GnRH neurons
excitatory neurotransmitters:
-glutamate
-NMDA
-kisspeptin
```
66
maturational changes in estradiol negative feedback to the hypothalamus
child: even a low level of steroids blocks the release of gonadotropins
adults: much higher levels occur
high sensitivity of gonadotropin release to negative feedback during childhood, low sensitivity during adulthood
67
changes in HPG prior to puberty
early nocturnal increases in gonadotropin secretion
68
HPG axis during sexual maturation (puberty)
first ovulation: E2 positive feedback and LH surge
initiation of menstural cycles
sexual maturity = establishment of patterns at the level of the hypothalamus, pituitary, ovary, and uterus + changes in phenotype and behavior
69
female secondary sex characteristics
```
breasts
pubic hair
growth spurt
changes in habitus
menarche
axillary hair
```
