Male reproductive system

Question 1

Process of LH and FSH secretion

Answer 1

1) Hypothalamus secretes Gonadotropin-releasing hormone (GnRH)
Pulsatile secretion (on and off)

2) GnRH bind to Anterior Pituitary cell, triggers secretion of LH and FSH
LH and FSH are protein hormones → bind to surface receptors
Receptor will be desensitised if hormone keeps binding to it

3) In testes, FSH binds to Sertoli cells, LH binds to Leydig cells
Sertoli → nutrients for spermatogenesis
Leydig → produce testosterone

4) (-) High level of testosterone sends (-) feedback to Hypothalamus and Anterior pituitary
Hypothalamus produce less GnRH
Anterior pituitary release less LH

5) (-) Sertoli cells secrete Inhibin
Inhibin selectively inhibits FSH

Question 2

Role of Sertoli cells and Leydig cells

Answer 2

Sertoli cells → provide nutrients for spermatogenesis
Leydig cells → produce testosterone

Question 3

How is DHT produced? And which enzyme catalyses the reaction?

Answer 3

Testosterone converted to DHT in Sertoli cells, catalysed by 5a reductase

Question 4

3 causes of infertility

Answer 4

1) Testicular —> Spermatogenesis, Hormones (T, DHT)
Failure in sperm production, hormone production
Trauma, infection, drugs intake, chromosomal abnormalities, developmental abnormalities
cryptorchidism,
congenital absence of seminiferous tubules, Sertoli cells and Leydig cells
Defective androgen biosynthesis

2) Post Testicular → Ducts, Accessory glands, Penis
Failure in sperm storage, transport, nourishment and release

3) Pre-testicular → HPT axis - hormonal control
GnRH deficiency, Gonadotropin (LH, FSH) deficiency, Pituitary tumour, Adrenal insufficiency, Androgen intake leading to dysregulation in (-) feedback

Question 5

Effect of Testosterone

Answer 5

Internal male genitalia differentiation
Muscle mass
Puberty, growth spurt
Penis growth
Libido
Deepening voice
Spermatogenesis

Question 6

Effect of DHT

Answer 6

EXTERNAL male genetalia differentiation
Sebaceous glands
Prostate growth
Male hair pattern baldness