Sex Steroids Part 1 Flashcards
What are 4 ways hormones communicate
think “crine”
- endocrine
- autocrine
- Paracrine
- juxtacrine
What type of sex hormone is testosterone
androgen
What type of compounds are all steroids?
lipophilic, low molecular weight
compounds
What do all steroid hormones derive from
A: cholesterol
What is the first enzymatic step for the production of steroid hormones and what are 2 sources of cholesterol
think changing cholesterol for first part
for second part think LDL and HDL, and enzymes in the cytosol
- enzymatic modification of cholesterol
2 sources are:
- Dietary sources delivered as a complex with Low density protein LDL and High density protein HDL
AND
- De novo biosynthesis starting from co- enzyme A in the cytosol
What is required for the biosynthesis of steroids?
think transportation of cholesterol into something of specific enzymes using a specific protein
Cholesterol being transported into the mitochondria of cells using the StAR protein where Cytochrome P450 enzymes act on it
What do the steroid hormones androgens do?
think something to do with male sexual characteristics
control expression and maintenance of male sexual characteristics
What are 3 examples of Androgens?
Adrenal androgens:
- DHEA and androstenedione
AND
- testosterone
What adrenal cortex region is aldosterone (mineralocorticoid) produced in
think letter g
Zona glomerulosa
What adrenal cortex region is cortisol (glucocorticoids) produced in
think f
Zona fasciculata
What adrenal cortex region is androgens (sex steroid prcursors) produced in
think r
Zona reticularis
Where is testosterone produced
think cells between something in the testes
> in Leydig cells lying in interstitial tissue between seminiferous tubules in the testes
Give 2 feature of the testes
think what they are and what they contain
- the male gonads
- consists of tubules that contain testosterone and sperm-producing cells
Where are Sertoli cells located?
- seminiferous tubules
How many weeks after human foetal development (soon after differentiation) do leydig cells produce testosterone and what is testosterone production stimulated by
think gonadotropins for second part
- 8 weeks
- stimulated by LH
What type of Leydig cells are the primary source of testosterone, foetal or adult-type?
- foetal type
What source of cholesterol synthesis do Leydig cells rely on
de novo cholesterol synthesis
outline what happens when Testosterone levels are low
think about GnRH, what it is released by, the pituitary gland and what this releases, and what these produces then stimulate
GnRH is released by the hypothalamus to stimulate pituitary gland to release FSH and LH which later stimulates the testis to synthesise testosterone
outline what testosterone does when levels increase
think feedback loops, hypothalamus and pituitary gland and GnRH and FSH/LH
through a negative feedback loop, testosterone will act on hypothalamus and pituitary gland to inhibit release of GnRH and FSH/LH respectively
What is the non specific carrier protein that transports almost any lipophilic molecule that enters the bloodstream
albumin
What are the 3 specific carrier proteins for different lipophilic molecules and what hormones are they specific for?
think corticoids, thyroid, and sex hormones
- CBG: specific for Glucocorticoids
- TBG: specific for Thyroid hormones
- SHBG: specific for oestradiol and testosterone
Where is SHBG mostly produced and what does the bioavailability of sex hormones depend on
think internal organs for first part
for second part think hormone levels
- mostly produced by liver
- bioavailability of sex hormones depends on SHBG levels
What is the binding affinity ranking list of SHBG to these hormones:
- TESTOSTERONE
- ANDROSTENEDIOL
- DHT
- OESTRONE
- OESTRADIOL
DHT > TESTOSTERONE >
ANDROSTENEDIOL >
OESTRADIOL > OESTRONE
What does increased levels of SHBG result in men and what does decreased levels of shbg result in in women
high levels of shbg in men: hypogonadism
decreased levels of shbg in women: androgenisation
