Lec3 Male and Female Reproductive Endocrinology Flashcards
In males, what does the release of GnRH from the hypothalamus cause?
Release of LH and FSH from the pituitary
What does LH do in males?
Acts on the testes to cause secretion of testosterone
What does FSH do in males?
Acts on the testes to cause sperm production
Which hormones are needed for sperm production?
Both LH and FSH because sperm production requires testosterone
What effect does testosterone have on GnRH, LSH and FSH?
Testosterone negatively feeds back on GnRH, release of LH and FSH therefore reducing the secretion of these three hormones
What effect does inhibin have?
Inhibin produced by the testes negatively feeds back to the anterior pituitary gland to stop production of inhibin
What are the effects of testosterone?
They cause the male secondary reproductive characteristics: Increased aggression & libido Enlargement of the larynx Male pattern pubic hair Muscle development Sperm production Bone growth Acne
How is testosterone conversion to oestrodiol?
Aromatase
During pregnancy, the mother produces lots of oestrogen, what effect does this have on the baby?
No effect on the development of the baby
What happens in the male embryo?
The testes of the male embryo start to secrete testosterone, which causes development of male foetal anatomy
If there is no hormone activity, what happens to the foetus?
Then it is by default a female embryo
What is required for male anatomy to develop in the foetus?
Testosterone
If an XY embryo cannot produce testosterone, what will happen?
He will be born with female anatomy
What happens to males during puberty?
There is a dramatic increase in testosterone secretion to allow male secondary reproductive characteristics to develop
In females, what happens when the hypothalamus secretes GnRH?
There is LH and FSH secretion from the anterior pituitary gland
What is the effect of LH secretion?
LH secretion causes progesterone to be secreted from the ovaries (progesterone is a single hormone)
What is the effect of FSH secretion?
FSH causes the ovaries to secrete oestrogen (oestrogens are a group of hormones)
What are progestogens?
Progestogens are a synthetic hormone used in contraception and are progesterone-like
What effect do oestrogen and progesterone have on LH and FSH?
Oestrogen and progesterone negatively feedback to reduce FSH and LH secretion respectively
What are the effects of oestrogen?
Oestrogen do not influence development
An increase in oestrogen production in females causes development of secondary sexual characteristics
What are the female secondary reproductive characteristics?
Bone growth Female psyche Fair complexion Breast development Widening of the pelvis Maturation of genitalia Female pattern pubic hair Subcutaneous fat deposition Ovulation and menstruation
What happens to the levels of oestrogen in puberty?
There is a dramatic increase of oestrogen production in females which causes the development of secondary female characteristics
The hormones are cyclical - not constant level
What other effects can oestrogen have?
Development of maternal instincts is due to oestrogen
What happens to oestrogen in menopause?
Women stop producing as much oestrogen and progesterone and lose some secondary characteristics LH and FSH secretion increase due to the loss of the negative feedback
Which hormone is dominant in the first half of the menstrual cycle?
Oestrogen
Which hormone is dominant in the second half of the menstrual cycle?
Progesterone
Why does this occur where there is oestrogen dominance in the first half and progesterone dominance in the second half?
Due to GnRH pulsatility - pulsatile secretion of GnRH
What decides whether there is FSH or LH secretion?
The frequency of the pulses
Slow pulses = FSH secretion
Fast pulses = LH secretion
How can we tell if a foetus is going to be female?
If there is a pulsatility pattern of GnRH secretion, can tell it is going to be a girl and what the pattern of the adult female menstrual cycle will be
If the female foetus is exposed to testosterone?
It will lose the GnRH pulsatility and it becomes constant - like in males
What is day 1 of the menstrual cycle?
First day of bleeding
What happens at the start of the menstrual cycle?
There is an increase in FSH secretion which causes a delayed increase in oestrodiol
What effect does the oestrodiol have on the FSH
The oestrodiol has a negative feedback effect on the FSH so FSH secretion dips and so oestrodiol secretion reduces as well
What happens at day 12?
There is a surge in LH over 24 hours and also a little surge in FSH - no function of FSH surge, just incidental
What is required to happen in order for there to be a LH surge?
There needs to be 36 hours of elevated oestrodiol for the LH surge to occur
What effect does the LH surge at day 12 have?
The LH surge causes an increase in oestrodiol secretion and progesterone secretion - LH is sufficient to cause the oestrodiol and progesterone increase for 7 days but there is vastly more progesterone than oestrodiol
What can be said about oestrogen concentration mid cycle?
There is a large variation in oestrogen concentration mid cycle
What happens in the few days mid cycle when progesterone and oestrodiol levels are very low?
Only in some people the oestrodiol levels come down to 0
In these few days of low oestrodiol and progesterone, the adrenals produce testosterone
What becomes the dominant hormone mid cycle and is increased in people with acne?
Testosterone
When the menstrual cycle extends in length, which half the first or second half stays constnat?
The second half - last 14 days - stay constant
The first half - first 14 days change
What effect does FSH have on the follicle in the process of ovulation?
The FSH causes the follicle to mature and secrete oestrogens
What happens during maturation of the follicle?
The ovum moves towards the edge of the follicle and during the LH surge (day12) is expelled from the follicle - causing ovulation at day 14
What happens after ovulation?
Following the expulsion of the ovum at day 14, the follicle turns yellow (lutenising) and produces lots of progesterone
When does ovulation occur?
On day 14 usually - or 14 days before the first day of menstruation
What effect does oestrodiol have on the endometrium?
It causes the endometrium to grow and thicken
If oestrodiol was present for longer, what would happen?
The endometrium would become thicker and thicker
What happens when progesterone is dominant?
The thickening of the endometrium ceases but enters ‘secretory’ phase where it secretes nutrients
The purpose of this is to support the ovum and allow it to grow if it is fertilised
If the ovulation doesn’t result in fertilisation, what happens when there is no stimulatory hormone and progesterone starts to drop?
The endometrial lining starts to collapse
Any drop in progesterone will result in?
The collapse of the endometrial lining
What does the drop in progesterone cause to happen to the blood vessels in the endometrium?
Causes them to vasoconstrict
What effect does vasoconstriction of the blood vessels have on the endometrium?
The tissue becomes hypoxic due to a lack of blood supply
After 18hours-3 days, the blood vessels dilate to the surrounding dead tissue, what effect does this have?
Increased blood supply causes the dead cells to be washed off
This causes clots which sit in the endometrium
Over the next couple of days the clot is broken down by:
fibrinolysis
What does the breakdown of the clot result in?
Menstruation
When the cells are anoxic and endometrial cells are dying what do they produce?
Inflammatory mediators e.g. prostaglandins
What do the prostaglandins cause?
Uterine contractions - period cramps and pain
What do Aspirin and NSAIDs do?
Inhibit prostaglandin synthesis?
Why are aspirin and NSAIDs thought to be helpful for period pain?
They inhibit prostaglandin synthesis so they prevent the induction of uterine contraction - reducing the cramping
Aspirin also has an anti-platelet effect which prevents the clots forming and increasing menstrual flow but this is not seen clinically
How does the cervix prevent bacteria from entering the sterile environment of the uterus but allow sperm to get in?
Oestrogen causes the cervix to dilate so at the time of ovulation the cervix is maximally dilated to allow fertilisation to occur
What effect does progesterone have on the cervix?
Causes it to constrict
What effect does oestrodiol have on the cervical mucus?
Reduces its viscosity - makes it thin and watery - to allow sperm to swim through but not bacteria
What effect does progesterone have on the cervical mucus?
Increases the viscosity to prevents sperm from getting through
What does progesterone cause the day after ovulation?
An increase in body temperature
What is the life expectancy of the ovum after ovulation
36-48hours
What is the lifespan of sperm?
Active lifespan of 2 days
What is the most fertile window for a woman?
Day 12- 16
What can be said of women with a low day 3 serum inhibin B?
They demonstrate a poorer response to ovulation induction and are less likely to conceive through ART relative to women with high day 3 inhibin B
The levels of day 3 inhibin B are used as what?
A measure of reproductive health
