REB Endocrine 2 Flashcards
What main gonadal hormones are produced by males
DHT and testosterone
What main gonadal hormones are produced by females
Estrogen and progesterone
There are several types of Estrogens produced by woman. What is the primary oestrogen in woman
estradiol
GNRH is released from the hypothalamus through
Pulsatile secretions
GNRH causes the release of what is hormones from the anterior pituitary?
Gonadotropins FSH and LH
Where does FSH go after being released by the anterior pituitary and what does it stimulate? (female)
Ovary
Estrogen production
Follicular development
When is LH released? (female)
After ovulation
What is the function of LH (female)
causes the secretion of progesterone and oestrogen production from the corpus luteum
maintains structure and secretory function of corpus luteum
high frequency pulse of GnRH causes the release of
FSH
low frequency pulse of GnRH causes the release of
LH
what is the function of progesterone?
converts endometrium to it’s secretory stage, prepares uterus for implantation
what cells secrete inhibin? where are these cells located?
granulosa cells
ovary
what does inhibin inhibit?
FSH secretion
what are the stages of the menstrual cycle?
- menses
- follicular phase
- ovulation
- luteal phase
what is menses
shedding of endometrium
important events of follicular phase
ovum maturation
endometrium proliferation (thickening)
increased estrogen levels
during the ovulation phase, there is a surge of
LH
the surge of LH during the ovulatory phase causes
rupture of follicle and small surge in FSH
in the luteal phase, there is an increase in
progesterone secretion
the increase of progesterone secretion in the luteal phase causes inhibition of release of
gonadotropins (by negative feedback)
what happens if there is no implantation in the luteal phase
progestesterone secretion stops
induces menses
what happens if there is implantation in the luteal phase
corpus luteum persists and continues to secrete progesterone
maintains pregnancy
what are the changes of body temperature observed after ovulation? what is the importance of this?
increased by 0.3°C
increases the chance of conceiving
FSH has a positive relationship with ___
LH has a positive relationship with ___
estrogen
progesterone
when do inhibin levels peak
after ovulation
what is the relationship between inhibin and estrogen levels
inversely proportional
what hormone aids in the development and maintenance of sex characteristics in females
estrogen
what are some common sex characteristics of females
breasts body hair sweat glands thigh muscles behind femur low hip-waist ratio more fat around butt, thigh, hips
what hormone controls ovarian and uterine cycles
estrogen
what hormone stimulates linear bone growth (puberty)
estrogen
what are the types of estrogens produced and in what quantity (%). in what stage of a female’s life is each type released
estrone - (E1) - 10% - menopause
estradiol - E2 - 80% - NORMAL
estriol - E3 - 10% - during pregnancy
estradiol regulates what phase of the menstrual cycle
follicular phase
estradiol is regulated by what hormone
FSH
other than ovaries, where is estrogen produced
adipose tissue
adipose tissue estrogen through what type of reaction. what enzyme catalyses this reaction?
aromatization
aromatase - CYP19a1
what type of estrogen is made in adipose tissue
estrone - E1
estrone is made from what hormone
androstenedione
what type of estrogen is made in ovaries
estradiol - E2
estradiol is made from what hormone
testosterone
what is the purpose of aromatase inhibitors
used to prevent estrogen from forming cancers in post-menopausal women
how does estrogen aid in fertility control
ovum maturation and development
the timing of the follicular phase is controlled by E2
how does estrogen aid in the preparation of the uterine wall
proliferation of the endometrial lining and induction of progesterone receptors to allow for progesterone sensitivity in the luteal phase
how does estrogen inhibit FSH release
by negative feedback on the ant pit
what is the metabolic action of estrogen
similar to mineralocorticoids
retention of Na+ and water
what is the action of estrogen on lipids
increases HDL in plasma
decreasing LDL and cholesterol concentration
estrogen increases blood coagulability by
increase in the number of clotting factors
what is the effect of estrogen on bone, skin and blood vessels
maintains bone density and elasticity of skin and blood vessels
progesterone is secreted by the ____ during the cycle and by ____ during pregnancy
corpus luteum
placenta
what is the function of progesterone
supports gestation and embryogenesis
maturation of the endometrium
gonadotropins are produced and secreted by
gonadotropes in the ant pit
or by the chorion and placenta during pregnancy
what are the gonadotropins produced
FSH
LH
HCG
what type of hormones are gonadotropins
glycoprotein
what subunits are in gonadotropins and what is their significance
alpha and beta
alpha is common
beta is different
LH and HCG have similar beta –> same target tissue –> same response (increase progesterone)
why can LH and HCG act on the same target tissue
similar B group
LH and HCG both increase the secretion of what hormone
progesterone
what controls the secretion of FSH and LH
GnRH and GnIH
negative feedback form androgens and estrogens
describe the pulses of GnRH in males and females
females - low f - FSH
high f - LH
male - constant pulses
describe GnRH activity in children
very low and is activated at puberty
what ant pit hormones do both males and females produce
FSH
LH –> ICSH
what is the function of FSH in males
targets sertoli cells to promote spermatogenesis
what is the function of ICSH or LH in males
causes secretion of testosterone and other androgens
testosterone is the precursor of
DHT
testosterone has negative feedback to the
AP and Hypothalamus
what is the result of too much testosterone
infertility
what is testosterone produced by
what hormone stimulates its release
interstitial cells
ICSH
interstitial cells convert testosterone to
what enzyme is used
DHT
5 alpha reductase
DHT is present at ___ the concentration of testosterone in plasma
1/10th
androstenedione is produced by the
adrenal cortex
the adrenal cortex produces androstenedione
what else does it produce
DHEA
what hormones are formed from testosterone and in what amounts (%)
DHEA (10%)
estradiol (0.3%)
Inactive metabolites (90%)
is androstenedione less potent than testosterone?
YUP
what hormone is a major source of androgens in females?
androstenedione
what are the common secondary sexual characteristics in males
muscles in thigh at front of femur shoulder wider than hips heavier skull and bones higher waist-hip ratio enlargement of larynx for deeper voice
what is the result of a 5 alpha reductase deficiency
no synthesis of DHT
- -> boys born with ambiguous external genitalia but will have normal ducts and internal structures
- things still develop normally at puberty
what is the importance of DHT in males
formation of male external genitalia during embryogenesis
CAH is a deficiency in
21OH and 11B-OH
what is the result of CAH
increased androgen production
- electrolyte imbalance
- salty urine
- early puberty in boys, ambiguous genitalia in girls
explain how hormones aid in the maintenance of the endometrial lining in pregnancy (start from the beginning of the cycle)
FSH –> estrogen –> estrogen burst –> increased LH –> ovulation –> corpus luteum –> estrogen and progesterone
after ovulation, the ovum is picked up by the ______ and enters the ______
fimbriae of fallopian tube
oviduct
where does fertilisation of the ovum occur
ampulla in the upper 1/3 of it
how long after ovulation can fertilisation occur?
24 hours
how long does sperm last in a female
48 hrs-5 days
how much sperm (%) gets to the uterus and how much gets to the ampulla
- 1%
0. 001%
the ovum is surrounded by how many layers?
2
what the layers surrounding the ovum? describe them
- corona radiata - yellow layer of follicular cells
2. zona pellucida - matrix of glycoproteins
fertilization occurs when the sperm binds to a ____ in the zona pellucida
sugar group
** ZP3 receptor
describe the steps of fertilization
- fertilizing sperm penetrates the corona radiata using enzymes found on its head and binds to the ZP3 receptor on the zona pellucida
- binding of sperm to the receptor triggers acrosome reaction where enzymes located in acrosome of sperm are released on the zona pellucida and digests it
- once the sperm reaches the ovum, the plasma membranes of the 2 cells fuse allowing the sperm nucleus into to the ovum cytoplasm
- the sperm stimulates release of CA2+ stored in cortical granules in the ovum which in turn inactivates ZP3 receptor, blocking sperm
what is the effect of the binding of sperm to the ZP3 receptor
triggers acrosome reaction where enzymes located in acrosome of sperm are released on the zona pellucida and digests it
in fertilisation, what mechanism prevents the binding of additionals sperm after the binding of the 2 nuclei
sperm stimulates release of CA2+ stored in cortical granules in the ovum which in turn inactivates ZP3 receptor, blocking sperm
to prevent the binding of additional sperm nuclei, the sperm which fertilised the ovum releases Ca2+. where is this Ca2+ stored?
cortical granules
3-4 days after fertilisation, the zygote remains in the ampulla and undergoes _____ to form a ____
mitotic divisions
morula
in the early stages of development, what stimulates the release of glycogen from the endometrium?
what is the function of this glycogen?
rising progesterone levels from the corpus luteum
fxn - energy source for embryo
in the early stages of development, what is the effect of rising progesterone levels from the corpus luteum
stimulates the release of glycogen from the endometrium
at what stage of development (DAYS) does the morula enter the uterus
3-4 days after ovulation