Male Hormonal Control of Reproduction and Infertility

Question 1

where is GnRH produced?

Answer 1

median eminence of hypothalamus.

Question 2

what happens to GnRH after it is secreted?

Answer 2

GnRH diffuses to pituitary

Question 3

what does GnRH cause?

Answer 3

release of gonadotropins (luteinising hormone (LH) & follicle stimulating hormone (FSH)).

Question 4

what does overstimulation of GnRH lead to?

Answer 4

gonadotropin depletion & deficiency.

Question 5

what does under stimulation of GnRH lead to?

Answer 5

inadequate gonadotropin production & deficiency.

Question 6

what cells does FSH act on in the male reproductive system?

Answer 6

Sertoli cells

Question 7

what are the effects of FSH on the male reproductive system?

Answer 7

production of Androgen Binding Protein (ABP) for transport of testosterone around blood. Also has a direct effect on germ cells (via the S. cells).

Question 8

what cells does LH act on in the male reproductive system?

Answer 8

Leydig cells

Question 9

what do the Leydig cells do?

Answer 9

produce testosterone

Question 10

what does testosterone act on?

Answer 10

testosterone stimulates germ cells directly but also acts on bone, skin, hair and accessory sexual organs

Question 11

what is testosterone converted to?

Answer 11

dihydrotestosterone

Question 12

what are the actions of dihydrotestosterone?

Answer 12

effects on prostate; and oestradiol – important in epiphysial closure and reproductive system.

Question 13

what is FHS negatively regulated by?

Answer 13

inhibin

Question 14

where is inhibin produced?

Answer 14

Sertoli cells at the level of pituitary

Question 15

what positively regulates FSH?

Answer 15

activin & follistatin

Question 16

what negatively regulates LH?

Answer 16

testosterone acting at level of pituitary and hypothalamus

Question 17

what is the cause of Kallman’s syndrome?

Answer 17

Defect – deletion or point mutation – in kal-1 gene, on X-chromosome.

Question 18

what is the function the kal-1 gene?

Answer 18

produces anosmin. Regulator of outgrowth of axons

Question 19

what happens to GnRH neurones in foetal life?

Answer 19

migrate from olfactory epith –> pituitary.

Question 20

what are the symptoms of Kallman Syndrome?

Answer 20

No release of gonadotropins –> hypogonadism – lack of secondary sexual characteristics. Azoospermia. Anosmia.

Question 21

what is the treatment for Kallmann syndrome?

Answer 21

Testosterone substitution

Pulsatile GnRH

Question 22

what is the cause of Kleinfelter syndrome?

Answer 22

XXY (Non-disjunction during meiosis.)

Question 23

what are the symptoms of Kleinfelter syndrome?

Answer 23

(Usually only after puberty)

Hypogonadism –> azoospermia

Androgen deficiency

Gynaecomastia (~50% of cases)

Learning difficulties

Question 24

how is Kleinfelter syndrome treated?

Answer 24

Life-long testosterone substitution.

Question 25

what is the cause of complete testicular feminisation?

Answer 25

X-linked recessive condition. Inactivation of androgen receptor. (Androgen resistance)

Question 26

what are the symptoms of complete testicular feminisation?

Answer 26

Small inguinal testes

Lack of axillary or pubic hair

1º amenorrhea

Phenotypically ♀; genotypically ♂

Question 27

how can complete testicular feminisation be treated?

Answer 27

Orchidectomy (to remove risk of testicular cancer)

Oestrogen substitution after puberty