Sex Steroids Part 1

Question 1

What are 4 ways hormones communicate

think “crine”

Answer 1

• endocrine
• autocrine
• Paracrine
• juxtacrine

Question 2

What type of sex hormone is testosterone

Answer 2

androgen

Question 3

What type of compounds are all steroids?

Answer 3

lipophilic, low molecular weight
compounds

Question 4

What do all steroid hormones derive from

Answer 4

A: cholesterol

Question 5

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

Answer 5

• 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

Question 6

What is required for the biosynthesis of steroids?

think transportation of cholesterol into something of specific enzymes using a specific protein

Answer 6

Cholesterol being transported into the mitochondria of cells using the StAR protein where Cytochrome P450 enzymes act on it

Question 7

What do the steroid hormones androgens do?

think something to do with male sexual characteristics

Answer 7

control expression and maintenance of male sexual characteristics

Question 8

What are 3 examples of Androgens?

Answer 8

Adrenal androgens:
- DHEA and androstenedione

AND

• testosterone

Question 9

What adrenal cortex region is aldosterone (mineralocorticoid) produced in

think letter g

Answer 9

Zona glomerulosa

Question 10

What adrenal cortex region is cortisol (glucocorticoids) produced in

think f

Answer 10

Zona fasciculata

Question 11

What adrenal cortex region is androgens (sex steroid prcursors) produced in

think r

Answer 11

Zona reticularis

Question 12

Where is testosterone produced

think cells between something in the testes

Answer 12

> in Leydig cells lying in interstitial tissue between seminiferous tubules in the testes

Question 13

Give 2 feature of the testes

think what they are and what they contain

Answer 13

1. the male gonads
2. consists of tubules that contain testosterone and sperm-producing cells

Question 14

Where are Sertoli cells located?

Answer 14

• seminiferous tubules

Question 15

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

Answer 15

• 8 weeks
• stimulated by LH

Question 16

What type of Leydig cells are the primary source of testosterone, foetal or adult-type?

Answer 16

• foetal type

Question 17

What source of cholesterol synthesis do Leydig cells rely on

Answer 17

de novo cholesterol synthesis

Question 18

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

Answer 18

GnRH is released by the hypothalamus to stimulate pituitary gland to release FSH and LH which later stimulates the testis to synthesise testosterone

Question 19

outline what testosterone does when levels increase

think feedback loops, hypothalamus and pituitary gland and GnRH and FSH/LH

Answer 19

through a negative feedback loop, testosterone will act on hypothalamus and pituitary gland to inhibit release of GnRH and FSH/LH respectively

Question 20

What is the non specific carrier protein that transports almost any lipophilic molecule that enters the bloodstream

Answer 20

albumin

Question 21

What are the 3 specific carrier proteins for different lipophilic molecules and what hormones are they specific for?

think corticoids, thyroid, and sex hormones

Answer 21

• CBG: specific for Glucocorticoids
• TBG: specific for Thyroid hormones
• SHBG: specific for oestradiol and testosterone

Question 22

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

Answer 22

• mostly produced by liver
• bioavailability of sex hormones depends on SHBG levels

Question 23

What is the binding affinity ranking list of SHBG to these hormones:
- TESTOSTERONE
- ANDROSTENEDIOL
- DHT
- OESTRONE
- OESTRADIOL

Answer 23

DHT > TESTOSTERONE >
ANDROSTENEDIOL >
OESTRADIOL > OESTRONE

Question 24

What does increased levels of SHBG result in men and what does decreased levels of shbg result in in women

Answer 24

high levels of shbg in men: hypogonadism

decreased levels of shbg in women: androgenisation

Question 25

What 2 main mechanisms do the effects of testosterone occur by

Think androgen receptors and oestradiol and oestrogen

Answer 25

• Activation of androgen receptor AR
• conversion to oestradiol and activation of oestrogen receptors

Question 26

What are the 3 distinct domains on the single polypeptide chain in Androgen receptors

Think the letter N, DNA and ligands

Answer 26

• N-terminal domain
• DNA binding domain DBD
• Ligand-binding domain

Question 27

What is the N-terminal domain

think variable sequences and transcription

Answer 27

Highly variable sequence involved in activating or stimulating transcription.

Question 28

What is the DNA binding domain (DBD)

##

Think binding and sequences of DNA

Answer 28

region responsible for binding of the receptor to specific sequences of DNA.

Question 29

What is the ligand binding domain

Think hormones

Answer 29

hormone binding region