Sex Steroid Hormones Flashcards
Where is GnRH released from?
The hypothalamus
What is the effect of GnRH?
Stimulates the synthesis and secretion of LH and FSH
Where is FSH released from?
The anterior pituitary
What is the effect of FSH?
Stimulates follicle growth and occyte maturation
Where is LH released from?
Anterior pituitary
What is the function of LH?
- Stimulates ovulation
- Causes the ruptured follicle to become the corpus luteum
Where is oestrogen released from?
Maturing follicle
What is the effect of oestrogen?
- It stimulates repair and growth of the endometrium
- Feedback inhibitor for FSH and LH
Where is progesterone released from?
Corpus luteum
What is the effect of progesterone?
- Prepares endometrium for implantation
- Promotes growth of mammary glands
- Feedback inhibitor for FSH and LH
Draw a diagram illustrating the feedback mechanism involved in reproductive hormones
How are sex steroid hormones transported?
Bound to SHBG (except progesterone) and albumin
What % of the sex hormones are free in the plasma?
1-2%
How is SHBG production regulated?
It is upregulated by oestrogen
What does SHBG binding to sex hormones protect against?
Hepatic metabolism - the binding prevents entry to the liver
Describe the liver metabolism of progesterone
It is almost totally metabolised in one passage through the liver in the first pass effect
What effect does storage of sex hormones have on the half life?
It increases it
Where can sex steroid hormones be easily stored?
In fatty tissue - adipocytes and brain
Why can sex steroids be easily stored in fatty tissue?
Because they are lipophilic
How are sex steroid hormones stored in fatty tissues?
They complex into the plasma membrane just like cholesterol
Does the complexing of sex steroid hormones into the membrane affect membrane fluidity?
Yes
How are the metabolites of sex steroid hormones excreted?
- In faeces as glucuronides
- In urine as sulphates
Why must the glucuronide from sex hormone metabolism be excreted in faeces?
As the molecule is too big to cross the plasma membrane, and so it passes into the bile duct
How are the sulphates produced from sex hormone metabolism excreted in urine?
They get ionised, pass through the body in the plasma, and then get picked up by clatherin coated pits in the kidney
How do sex steroid hormones exert their effects?
Through binding to nuclear receptors
What are the types of oestrogen receptors?
ER-alpha and ER-beta
Truncated forms exist in cancer