Male Sex Hormones

Question 1

what is testosterone?

Answer 1

a potent androgen

Question 2

where is testosterone synthesised?

Answer 2

within the leydig cells of testes in males and some adrenal cortex cells in both males and females

Question 3

what is testosterone responsible for?

Answer 3

the development and maintenance of the male secondary sexual characteristics e.g. hair growth
-activate oestrogen receptors

Question 4

what two other androgens are synthesised in the adrenal cortex in both genders besides testosterone?

Answer 4

1. dehydroepiandrosterone (DHEA) - causes early pubic hair growth in boys and girls
2. Androstenedione
   - both are weak androgens

Question 5

what is testosterone metabolised to in men?

Answer 5

• dihydrotetosterone with the use of the enzyme 5alpha-reductase (types 1&2)
• this is an active testosterone metabolite

Question 6

what is testosterone metabolised to in women?

Answer 6

• estradiol with the use of aromatase enzyme.

- estradiol is an active metabolite of testosterone

Question 7

what does testosterone do in men?

Answer 7

1. stimulates testes enlargement and male accessory organ

2. Stimulates development of male secondary sex characteristics

Question 8

what are the male secondary sex characteristics?

Answer 8

1. increased body hair growth
2. Enlargement of the larynx and thickening of the vocal cords
3. Thickening of the skin
4. Muscle growth, widening of shoulders, narrowing of waist
5. Thickening and strengthening of bones

Question 9

how does DHT work?

Answer 9

• binds to cytoplasmic androgen receptors which promotes release of heat shock protein.
• it then migrates to the nucleus where it binds to specific regions of DNA that contain androgen response elements (ARE)
• this drives the expression of genes that determine male phenotype

Question 10

what is the effect of androgen receptor insensitivity in women?

Answer 10

the women develop normally with very sparse pubic and axillary hair

Question 11

where are male reproductive hormones released?

Answer 11

1. hypothalamus
2. anterior pituitary glad
3. testes

Question 12

what is the function of male reproductive hormones?

Answer 12

– Development of sperm cells

– Development of secondary sex characteristics

Question 13

In both genders the brain controls reproduction through which hormones?

Answer 13

1. GnRH (gonadotropin releasing hormone)

2. Pituitary gonadotropins (e.h. FSH and LH)

Question 14

where is GnRH produced?

Answer 14

by the hypothalamus

Question 15

what 2 hormones does GnRH drive the release of from the anterior pituitary?

Answer 15

FSH and LH

Question 16

how does LH work?

Answer 16

Luteinising hormone works to activate leydig cells in seminiferous tubules evoking testosterone release into the bloodstream

Question 17

how does FSH work?

Answer 17

• acts on Sertoli cells which release androgen binding protein (ABP) into the lumen
• this binds to testosterone leading to its accumulation in seminiferous tubules
• FSH also stimulates inhibin production

Question 18

what effect does a very high testosterone level have?

Answer 18

it drives spermatogenesis

Question 19

what does inhibin do to the body?

Answer 19

• mediates the negative feedback to suppress FSH and LH release.
• testosterone also suppresses them

Question 20

what 3 things does testosterone suppress the production of?

Answer 20

1. GnRH
2. LH
3. FSH

Question 21

what are exogenous androgens?

Answer 21

the anabolic steroids used by body builders

Question 22

what is the effect of repeated use of an anabolic steroid?

Answer 22

• causes abnormally high levels of androgen so GnRH, FSH and LH release is suppressed
• this suppresses endogenous testosterone production
• FSH can’t stimulate androgen binding protein (ABP) so spermatogenesis is inhibited

Question 23

what is abnormally high testosterone metabolised to in anabolic steroid users?

Answer 23

oestrogen

Question 24

what is the effect of withdrawing from the exogenous anabolic steroid?

Answer 24

causes gynecomastia (an increase in the amount of breast gland tissue in boys or men)

Question 25

what happens to penile arterioles to cause an erection?

Answer 25

they vasodilate to allow more blood through hence causing an erection

Question 26

what is the effect of testicular failure?

Answer 26

causes:

• infertility
• hypogonadism (reduction or absence of hormone secretion or other physiological activity of the testes or ovaries)
• and a lack of 2nd sexual characteristics
• can trat 2nd sexual characteristics but not fertility

Question 27

what is hypogonadotropic hypogonadism?

Answer 27

Infertility + associated hypogonadism and lack of 2nd sexual characteritics
-however, can treat 2nd sexual characteristics and improve fertility

Question 28

what is primary hypogonadism?

Answer 28

issues with the testes themselves

Question 29

what is secondary hypogonadism?

Answer 29

issues with the pituitary/hypothalamus

Question 30

what is the effect of hypogonadism in foetal life?

Answer 30

-causes impaired development of male genitalia

Question 31

what is the effect of hypogonadism during puberty?

Answer 31

delays puberty and causes longer limbs in relation to the rest of the body

Question 32

what is the effect of hypogonadism during adult life?

Answer 32

as you age, testosterone levels drop causing erectile dysfunction, infertility, less beard and body hair, development of breast tissue

Question 33

what are the testosterone replacement therapies available?

Answer 33

1. exogenous testosterone given by injection

2. transdermal patches of gels.