Male Hormonal Control of Reproduction and Infertility Flashcards
where is GnRH produced?
median eminence of hypothalamus.
what happens to GnRH after it is secreted?
GnRH diffuses to pituitary
what does GnRH cause?
release of gonadotropins (luteinising hormone (LH) & follicle stimulating hormone (FSH)).
what does overstimulation of GnRH lead to?
gonadotropin depletion & deficiency.
what does under stimulation of GnRH lead to?
inadequate gonadotropin production & deficiency.
what cells does FSH act on in the male reproductive system?
Sertoli cells
what are the effects of FSH on the male reproductive system?
production of Androgen Binding Protein (ABP) for transport of testosterone around blood. Also has a direct effect on germ cells (via the S. cells).
what cells does LH act on in the male reproductive system?
Leydig cells
what do the Leydig cells do?
produce testosterone
what does testosterone act on?
testosterone stimulates germ cells directly but also acts on bone, skin, hair and accessory sexual organs
what is testosterone converted to?
dihydrotestosterone
what are the actions of dihydrotestosterone?
effects on prostate; and oestradiol – important in epiphysial closure and reproductive system.
what is FHS negatively regulated by?
inhibin
where is inhibin produced?
Sertoli cells at the level of pituitary
what positively regulates FSH?
activin & follistatin
what negatively regulates LH?
testosterone acting at level of pituitary and hypothalamus
what is the cause of Kallman’s syndrome?
Defect – deletion or point mutation – in kal-1 gene, on X-chromosome.
what is the function the kal-1 gene?
produces anosmin. Regulator of outgrowth of axons
what happens to GnRH neurones in foetal life?
migrate from olfactory epith –> pituitary.
what are the symptoms of Kallman Syndrome?
No release of gonadotropins –> hypogonadism – lack of secondary sexual characteristics. Azoospermia. Anosmia.
what is the treatment for Kallmann syndrome?
Testosterone substitution
Pulsatile GnRH
what is the cause of Kleinfelter syndrome?
XXY (Non-disjunction during meiosis.)
what are the symptoms of Kleinfelter syndrome?
(Usually only after puberty)
Hypogonadism –> azoospermia
Androgen deficiency
Gynaecomastia (~50% of cases)
Learning difficulties
how is Kleinfelter syndrome treated?
Life-long testosterone substitution.
