The Gonads 2 Flashcards
Testosterone can act as a precursor which can follow two different reactions to produce other hormones
What are the names of the enzymes which converts them into the hormones and what are the names of these hormones?
What can testosterone be reduced into?
Name the enzyme responsible for this reduction as well?
State what is the difference between the new hormone produced by testosterones reduction?
Testosterone can be reduced to form DIHYDROTESTOSTERONE (DHT) which is far more potent but will still work on the SAME androgen receptors
DHT will be produced in target tissue that has the 5a-reductase enzyme
Testosterone can be aromatised to form …………………..
testosterone can be aromatised to form OESTROGENS
How Do Men Naturally Make Estrogen?
Women synthesize most of their estrogen in their ovaries and other reproductive tissues.
Since men lack this female anatomy, they need to produce estrogen through a process involving an enzyme called aromatase that transforms testosterone into estradiol.
The aromatase enzyme can be found in many tissues including gonads (granulosa cells), brain, adipose tissue, placenta, blood vessels, skin, and bone
What hormone is responsible for the virulising features in men?
Dihydroxytestosterone
Why are obese men more likely to develop gynecomastia?
You have increased peripheral converion of androgens to oestrogens which can lead to gynecomastia?
What effects does high oestrogen have on males?
List 5 places where 5 alpha reductase is found?
List 5 places where aromatase is found?
What hormones can testosterone be converted into?
DHT and Oestrogen
Why is it important to have 5 alpha reductase in skin?
Promotes facial hair growth
However can cause boldness
How are testosterone and DHT transported around the blood?
How is testoterone transported in the seminiferous fluid?
Androgen Binding Globulin
What proportion of Testosterone is bound to
SHBG
ALBUMIN
FREE
What organ makes SHBG?
Liver
What are the principal actions of Androgens on the Fetus?
What happens if you have an abscence of fetal testosterone?
Baby will be born with ambigous genitalia
the scrotum and labia are kind of equivalent
List 8 effects of androgens on adults?
Define Oestrogen?
List 6 effects of oestrogen ( repriduction)?
List 7 non-reproductive effects of oestrogen?
Increased salt and water reabsorption - women weight vary slighlt during the cycle
Increased plasma protein synthesis (hepatic effect)- if you are on the pill then if you require any liver metabolise drug, it will effect the dose of other drugs.
Metabolic actions (e.g. on lipids)
Tend to increase HDL levels- that is why women are less likely to have cardiovascular problems
Menopause - oestrogen levels are low so carbohydrate and lipid metabolism will be affected - women will become more susceptible to cardiovascular problems
Stimulates osteoblasts (androgens also do this)
Influences the release of other hormones (e.g. prolactin, thyrotrophin)
Behavioural effects
Feedback regulation (negative and positive)
Define Progestogens?
List 5 effects of progestogens?
Draw the HYPOTHALAMO-PITUITARY-TESTICULAR AXIS
Summary:Endocrine control of testicular function
The tesosterone and LH is needed for complete spermatogenesis. They are symbiotic
Draw the hypothalamo-pituitary-ovarian axis
What happens during the early follicular stage?
State what the levels of oestrogen and progesterone are and what effect does it have?
Early Follicular Phase - beginning of the menstrual cycle
Oestrogen and progesterone levels are low so there is little negative feedback so there is an increase in the production of LH and FSH and GnRH
LH and FSH start stimulating the development of some follicles in the ovaries
There is a little rise in 17a-hydroxyprogesterone during ovulation
What happens during the EARLY-MID FOLLICULAR PHASE?
Talk about the levels of hormones?
There is no further increase in FSH or LH
Oestrogen levels are beginning to rise dramatically (increases in the blood and in the ovaries)
Progesterone does NOT change
Draw a diagram showing the realtionship between thecal cells and granulosa cells?
There is no further increase in FSH or LH
Oestrogen levels are beginning to rise dramatically (increases in the blood and in the ovaries)
Progesterone does NOT change
Ovary: Local positive feedback loop in developing follicles enhances oestradiol production
THECAL cell = LH Receptor
GRANULOSA cell = FSH Receptor
Thecal cells respond to LH by increasing androgen production
Thecal cells work somewhat like Leydig cells in the testes
FSH binds to the FSH receptors on the Granulosa cells which activates AROMATASE
Aromatase converts androgens (from thecal cells) to 17b-oestradiol
At the beginning, FSH and LH levels are high causing a rise in oestrogen levels
Oestrogens produced by the granulosa cells will bind to the oestrogen receptor on the same granulosa cell and stimulate the aromatase enzyme via a second messenger system = AUTO-POSITIVE FEEDBACK
This means that the more oestrogen is produced by androgens, the more oestrogen is produced overall due to the positive feedback
- Rising levels of plasma E2( 17 beta oestradiol) causes stimulates ………………. cell growth
- More ……………… cells = more ability to synthesise E2
- Rising levels of plasma E2 causes stimulates granulosa cell growth
- More granulosa cells = more ability to synthesise E2
Because the oestrogen is rising it lowers the gonadotrophins- this causes the growing follicles suppress your pituitary and what this means is that the smaller follicle die and one of them become autonomous and survive without gonadotrophins
The Graafian Follicle
- The largest follicle no longer requires ……… to develop and proliferate
- It keeps growing and producing large amounts of ……..
- It is called the Graafian follicle
- Extremely high levels of …… from the Graffian Follicle results in the positive feedback on …………….. secretion
- The largest follicle no longer requires FSH to develop and proliferate
- It keeps growing and producing large amounts of E2
- It is called the Graafian follicle
- Extremely high levels of E2 from the Graffian Follicle results in the positive feedback on GnRH / LH secretion
Mid Follicular Stage
At this point the rising oestrogen levels have a negative feedback effect on ……..
Within the follicles, there are developing ova which are at different stages of development
A lot of these follicles are ……… dependent so by removing……., you kill the cells which are still …….. dependent (ATRESIA)
There is usually only ……… OVUM which can grow under its own production of local oestrogens and this is the ……………… FOLLICLE
Selective negative feedback loop by oestrogen and inhibin on the GnRH-FSH system results in ………………. of all follicles that are still FSH dependent: GRAAFIAN follicle survives
At this point the rising oestrogen levels have a negative feedback effect on FSH
Within the follicles, there are developing ova which are at different stages of development
A lot of these follicles are FSH dependent so by removing FSH, you kill the cells which are still FSH dependent (ATRESIA)
There is usually only ONE OVUM which can grow under its own production of local oestrogens and this is the GRAAFIAN FOLLICLE
Selective negative feedback loop by oestrogen and inhibin on the GnRH-FSH system results in ATRESIA (regression) of all follicles that are still FSH dependent: GRAAFIAN follicle survives
There is …………….. ……………. initially which is mainly due to inhibin acting on FSH
LH will still be produced to stimulate the production of ………………. but FSH is inhibited
The selective negative feedback is specifically on FSH
There is negative feedback initially which is mainly due to inhibin acting on FSH
LH will still be produced to stimulate the production of androgens but FSH is inhibited
The selective negative feedback is specifically on FSH
Ovarian hormones-negative feedback
Late Follicular Stage
At this stage we have had high oestrogen in the absence of progesterone for long enough to induce an LH surge
The LH surge at this point is sufficiently high to overcome the FSH negative feedback and so you get a lesser FSH surge
What happens if fertilization doesn’t occur?
If fertilization does not occur, progesterone, E2 and inhibin exert a negative feedback on LH and FSH release, causing luteolysis and menstruation
Luteolysis (also known as luteal regression) is the structural and functional degradation of the corpus luteum (CL), which occurs at the end of the luteal phase of both the estrous and menstrual cycles in the absence of pregnancy.
After ovulation, the cells of the follicle collapse to form a corpus luteum
The corpus luteum has cells which still have ……… and …….. Receptors
As oestrogen and progesterone levels fall after ovulation, there is initially FSH and LH being released
This stimulates the corpus luteum to produce more …………………. and ……………………………
…………………. and ……………….. levels will increase which exerts a negative feedback effect on the hypothalamo-pituitary axis
…….. and …… levels will decrease as they get inhibited by the increased negative feedback (mainly from PROGESTERONE)
Unless something happens to produce …… and ….., as the levels fall away, the corpus luteum will no longer be stimulated to produce OESTROGEN and PROGESTERONE
So oestrogen and progesterone levels begin to fall
As these levels fall, the negative feedback on the hypothalamo-pituitary axis is reduced so LH and FSH levels start to RISE again so they can reach a critical level at the start of the cycle again
After ovulation, the cells of the follicle collapse to form a corpus luteum
The corpus luteum has cells which still have FSH and LH Receptors
As oestrogen and progesterone levels fall after ovulation, there is initially FSH and LH being released
This stimulates the corpus luteum to produce more oestrogen and progesterone
Oestrogen and progesterone levels will increase which exerts a negative feedback effect on the hypothalamo-pituitary axis
FSH and LH levels will decrease as they get inhibited by the increased negative feedback (mainly from PROGESTERONE)
Unless something happens to produce FSH and LH, as the levels fall away, the corpus luteum will no longer be stimulated to produce OESTROGEN and PROGESTERONE
So oestrogen and progesterone levels begin to fall
As these levels fall, the negative feedback on the hypothalamo-pituitary axis is reduced so LH and FSH levels start to RISE again so they can reach a critical level at the start of the cycle again
Define Amenorrhoea?
Define Primary Amenorrhoea?
Define Secondary Amenorrhoea
Definition : absence of menstrual cycles
- primary if a women never had a single period
- secondary if a women has had periods which then stop
Some causes of primary amenhorroea
Some causes of secondary amenhorroea?
Define Infertility and list 5 main cause?
1 in 10 couples have infertility
PCOS- most common endo problem in women- more than diabetes aslong as you have 2 out of the 3 symptoms ( which are in small print at the bottom of the page) you have PCOS
