Module 2.4 Hormonal Control in Males

Question 1

Leydig cells convert ______ to _______

Answer 1

Leydig cells convert cholesterol to testosterone

Question 2

Describe the synthesis of Testosterone

Answer 2

Cholesterol is converted to pregnenolone via cholesterol side-chain cleavage enzyme

Pregnenolone is converted to progesterone via 3-beta-hydroxysteroid dehydrogenase

Progesterone is converted to androstenedione via 17-hydroxyprogesterone

Androstenedione is converted to Testosterone via 17-beta-hydroxysteroid dehydrogenase

Question 3

Testosterone is secreted by the ________ and can be converted to Dihydrotestosterone (DHT) via the enzyme _______

Answer 3

Testosterone is secreted by the testes and can be converted to Dihydrotestosterone (DHT) via the enzyme 5-alpha-reductase

Question 4

Where in the testosterone synthesis chain is Estrone and Estradiol synthesized?

Answer 4

• Estrone:
  
  • After Progesterone is converted to Androstenedione, Androstenedione is converted to Estrone via aromatase
• Estradiol
  
  • After Androstenedione is converted to Testosterone, Testosterone is converted to Estradiol via aromatase

Question 5

What is the pulsatile release of GnRH?

Answer 5

GnRH is secreted from the hypothalamus every 90min

Question 6

Where does GnRH act and via which portal vessels?

Answer 6

GnRH acts on the Anterior Pituitary via hypothalamohypophyseal portal vessels

Question 7

GnRH triggers __________

Answer 7

GnRH triggers pulsatile LH and FSH release

• slow removal from the plasma

Question 8

FSH acts on _________ to elicit _______

Answer 8

FSH acts on sertoli cells to elicit spermatogenesis

Question 9

LH acts on ______ to elicit _______

Answer 9

LH acts on Leydig cells to elicit Testosterone secretion

• Testosterone diffuses to seminiferous vesicles
• Enters sertoli cells to facilitate spermatogenesis

Question 10

Fill in the flow chart

Answer 10

Question 11

In which tissues is testosterone converted to estradiol and by means of which enzyme?

Answer 11

In the brain, liver, adrenal, muscle and adipose tissue

via enzyme aromatase

Question 12

What happens to testosterone in the prostate?

Answer 12

In the prostate, testosterone is converted to dihydrotestosterone (DHT) via 5-alpha-reductase

DHT is more potent and is responsible for secondary sex characteristics

Question 13

What are three components that could contribute to male infertility

Answer 13

Low sperm count

Sperm transport

Evironmental factors

Question 14

What is the leading cause of male infertility?

Answer 14

Low sperm count (oligospermia)

Absence of sperm (azoospermia)

Question 15

Oligospermia can be related to central nervous system dysfunction in what way?

Answer 15

Oligospermia (low sperm count) can be related to lower than normal function of hypothalamus and/or pituitary gland

Question 16

What are four treatment options for oligospermia?

Answer 16

Low sperm count

Tx:

1. GnRH stimulatory agonists
2. Gonadotropins
3. Anti-estrogen drugs
   
   • estrogen decreases GnRH and LH/FSH in males
4. Prolactin antagonists
   
   • Pituitary tumour - prolactin decreases GnRH

Question 17

Oligospermia may be related to dysfunction in the testes, how?

Answer 17

• Testes may not respond to gonadotropins (FSH/LH)
  
  • Structural abnormalities – surgical correction (eg restore bloodflow)
  • Permanent damage
    
    • no production of viable sperm
    • Chemotherapy or radiation — irreversible damage

Question 18

What is a varicocele?

Impacts?

Answer 18

Varicose vein in the scrotum

• Impacts:
  
  • As this testicular vein grows it increases pressure in the scrotum
  • Also increases heat (reduces temperature control) which decreases spermatogenesis

Question 19

What is cryptorchidism? How might it lead to oligospermia?

Answer 19

a condition in which one or both of the testes fail to descend from the abdomen into the scrotum.

• testosterone production is intact but spermatogenesis requires a cooler temperature than physiological temp

Question 20

What is Orchitis?

Answer 20

Testicular inflammation

• temporary or permanent infertility
• Infection

—- STIs, bacterial/viral (eg mumps)

Question 21

In which case would a treatment with adrenal hormones help to restore fertility?

Answer 21

In the case of autoantibodies to sperm

• treatment with adrenal hormones (cortisol) suppresses immune overactivity

Question 22

What types of sperm transport complications could interfere with fertility?

Answer 22

1. Improper development/function of secondary accessory ducts
   
   • Vas deferens
     
     • Occlusion by testicular vein
     • Scar tissue
   • Both require surgical correction
2. Malfunction or inactivity of secondary accessory gland
   
   • underdevelopment
     
     • Androgen treatment
   • Prostate infection “prostititis”
     
     • Sterility

Question 23

What are five environmental factors that might contribute to temporary or permanent infertility?

Answer 23

1. Smoking
   
   • decreases motility
   • increased number of structurally abnormal sperm
   • Lower T levels
2. Pollution
   
   • Heavy metals
   • industrial chemicals
   • endocrine disruptors (eg xenoestrogens/phytoestrogens)
3. Chronic drug use:
   
   • Alcohol, marijuana (both decrease GnRH = decrease HPG cascade)
   • Anabolic steroids
4. Age
5. Heat

Question 24

How can the abuse of anabolic steroids (synthetic androgens) be a cause of infertility?

Answer 24

• Overstimulate prostate = prostate cancer
• Aggression
• Decreased GnRH, LH, FSH
  
  • decrease in endogenous testosterone and spermatogenesis in sertoli cells
    
    • synthetic androgens DO NOT gain access to seminiferous tubules
  • Decreased testicular size, low sperm count
  • Addictiveness