Male Hypogonadism Flashcards
what stimulates release of GnRH from the hypothalamus?
kisspeptin
what does GnRH do?
stimulates the anterior pituitary to release LH and FSH
what effect do LH and FSH have in males?
testes stimulated to produce testosterone
what cells produce testosterone and what hormone controls this?
leydig cells
LH
how does the majority of testosterone exist?
bound to SHBG and albumin
only <2% free and bioavailable
what two things is testosterone converted to?
dihydrotestosterone
oestradiol
what is the highly active form of testosterone?
dihydrotestosterone
what breaks down dihydrotestosterone?
5a reductase
what breaks down oestradiol?
aromatase
what is male hypogonadism?
low or reduced testicular function
clinical syndrome of testosterone deficiency
what type of male hypogonadism is caused by a problem with the testes?
primary
what type of male hypogonadism is caused by a problem with the hypothalamus or pituitary?
secondary
what hormone level abnormalities are seen in primary hypogonadism?
low testosterone
raised LH/FSH
what is another name for primary hypogonadism?
hypergonadotrophic hypogonadism
how can primary hypogonadism present and why?
to fertility clinics, as spermatogenesis is affected
name three congenital causes of primary hypogonadism
klinefelte’s syndrome
cryptorchidism
Y chromosome microdeletions
name some acquired causes of primary hypogonadism
testicular trauma chemotherapy varicocele orchitis infiltrative disease medications
name an infiltrative disease that can cause primary hypogonadism
haemochromatosis
what type of infection can commonly cause orchitis?
mumps
name two medications that can cause primary hypogonadism
glucocorticoids
ketoconazole
what causes klinefelter’s syndrome?
nondisjunction
47 XXY
how is klinefelter’s syndrome diagnosed?
karyotyping
how does klinefelter’s syndrome present?
infertile
small, firm testes
what is there an increased risk of in patients with klinefelter’s syndrome?
cryptorchidism
learning disablities
breast cancer
non-hodgkin lymphoma
describe the hormone levels seen in secondary hypogonadism
low/inappropriately normal LH/FSH
low testosterone
what is another name for secondary hypogonadism?
hypogonadotrophic hypogonadism
name two congenital causes of secondary hypogonadism
kalman’s syndome
prader willi
what is another name for kalman’s syndrome?
isolated hypogonadotrophic hypogonadism
name some acquired causes of secondary hypogonadism
pituitary damage hyperprolactinaemia diabetes medications acute illness eating disorders
name two medications that can cause secondary hypogonadism
steroids
opioids
what is kalman’s syndrome?
a genetic disorder characterised by isolated GnRH deficiency and hyposmia/anosmia
what other abnormalities may be seen in kalman’s syndrome due to isolated GnRH deficiency?
unilateral renal agenesis
red-green colour blindness
cleft lip
bimanual synkinesis
how does hypogonadism present if onset is pre puberty?
small sex organs decreased body hair high pitched voice low libido gynaecomastia decreased bone + muscle mass
how does hypogonadism present if onset is post puberty?
normal sexual organs decreased libido + spontaneous erections decreased body hair decreased testicular volume gynaecomastia
what is the initial test for hypogonadism?
AM testosterone
repeated if low
how is testosterone measured?
total testosterone and SHBG measured and used to calculate the calculated free testosterone
when should testosterone be measured and why?
between 8-11am
peaks in the morning
how is male hypogonadism managed?
testosterone replacement therapy
what are the four contraindications to testosterone replacement therapy?
hormone responsive cancer
possible prostate cancer
haematocrit >50%
severe sleep apnoea/heat failure
