B8-006 Male Endocrinology Flashcards
stimulates leydig cells
LH
stimulates sertoli cells
FSH
testosterone inhibits […] and […] release from the pituitary gland
GnRH
LH
inhibin B inhibits […] release from the pituitary gland
FSH
[…] cells produce testosterone
Leydig
leydig cells express […] receptors
LH
sertoli cells express […] receptors [2]
FSH
androgen
[…] cells produce anti-mullerian hormone, androgen binding protein, and inhibin B
sertoli
[…] inhibits LH secretion in males
nicotine
(lowers testosterone levels)
factors that stimulate GnRH release [3]
NE
neuropeptide Y
leptin
factors that inhibit GnRH release [4]
IL-1
GABA
dopamine
prolactin
does LH or FSH have a longer half life?
FSH
[LH/FSH] higher amplitude pulses in plasma
LH
(FSH pulses are more stable due to longer half life)
both LH and […] bind to the same LH receptors on Leydig cells
hCG
[…] is secreted episodically in response to LH with about a 40 min lag
testosterone
what time of day does testosterone peak?
early morning
[…] levels of LH is expected with precocious puberty, primary testicular failure, and castration
high
[…] levels of LH is expected with Kallman syndrome, hyperprolactinemia, and primary pituitary failure
low
key rate limiting step in steroid hormone biosynthesis
steroidogenic acute regulatory protein (StAR)
(in mitochondria)
3 key symptoms of low testosterone
decreased morning erections
erectile dysfunction
decreased frequency of sexual thoughts
main function is to suppress the secretion of FSH from pituitary
inhibin B
(secreted from sertoli cells)
[…] cells secrete inhibin B
sertoli
[…] serums levels are a direct marker of sertoli cell function and correlate with both testicular volume and sperm production
inhibin B
normally inhibin B levels in males rise during puberty, however in […] syndrome they fail to rise due to testicular dysgenesis
Klinefelter
how do anabolic steroids cause infertility and shrinkage of testicles?
reduces LH secretion –> less testosterone produced
is testosterone bound to SHBG biologically active?
no
only free testosterone and albumin-bound are biologically available
describe SHBG levels throughout early life
fetal: low
childhood: high
puberty: low
adulthood: slowly rises over time
conditions that increase the amount of SHBG
hyperthyroidism
low GH
cirrhosis
stress
smoking
anti-seizure medications
essential for maintaining function of epididymis
androgen binding protein (sertoli cells)
the majority of estradiol in males is produced in […] tissue
adipose
(via aromatization of testosterone)
generates 3 times as much DHT and is critical for differentiation of male external genitalia
type II 5-a-reductase
5-a-reductase inhibitor used in treatment of BPH
finasteride
finasteride is sold under the brand name […] for BPH and […] for androgenic alopecia
proscar
propecia
controls sexual differentiation via development of the mesonephric duct structures
testosterone
defects of 5-a-reductase typically result in defects of
external genitalia
enzyme responsible for epiphyseal plate closure
aromatase
[…] virus replicates in Leydig cells and causes a decrease in testosterone production, can lead to infertility
mumps
LH and FSH will be high trying to stimulate T
FSH and LH concentrations remain significantly increased for […] months after acute phase of mumps
10-12
(testosterone lowers in acute phase but returns to baseline relatively quickly)
when are the 3 peaks on testosterone levels through the male lifetime?
fetal 12-18 weeks
neonatal 1 month
30 years old
[…] seems to be essential for the increased GnRH pulse secretions leading to puberty
leptin
precocious puberty is defined as the appearance of secondary sex characteristics before age […]
9
(rare in males)
[…]gonadotropic hypogonadism results from dysfunction at the level of the hypothalamus
hypo
(kallman)
[…]gonadotropic hypogonadism results from dysfunction at the level of the testis
hyper
(klinefelters)
[…] syndrome is characterized by delayed/absent puberty and impaired sense of smell
Kallmann
due to impaired migration of GnRH neurons from olfactory bulb to AVPV
inheritance pattern of Kallman’s syndrome
X linked recessive
high levels of prolactin inhibit […] release
GnRH
describe testosterone, LH, and FSH levels in Kallmanns
all low
describe testosterone, LH, and FSH levels in Klinefelters
testosterone: low
LH: high
FSH: high
testicular dysgenesis due to 47XXY
defect in androgen receptor resulting in female-appearing genetic male
complete androgen insensitivity syndrome
female external genitalia present
functioning testis present
no internal male/female genitalia
complete androgen insensitivity syndrome
genetic condition in which male has extra Y chromosome
jacob’s syndrome
double Y syndrome
risks of testosterone replacement therapy [4]
prostate disease (BPH or cancer)
polycythemia
sleep apnea
gynecomastia
male 47 XXY
klinefelter syndrome
small, firm testes
tall stature with long limbs
gynecomastia
female hair distribution
may have developmental delay
klinefelter syndrome
presence of inactivated X chromosome (Barr body)
relatively common cause of infertility see in workup
klinefelter syndrome
describe levels of inhibin B, FSH, Testosterone, and LH in klinefelter’s syndrome
inhibin B: low
FSH: high
T: low
LH: high
phenotypically normal
very tall
normal fertility
may be associated with acne or learning disability
Jacobs syndrome (XYY)
in hypogonadotropic hypogonadism, Testosterone will be […], and LH will be […]
T: low
LH: low
in hypergonadotropic hypogonadism, Testosterone will be […], and LH will be […]
T: low
LH: high
in exogenous androgenic steroid use, Testosterone will be […], and LH will be […]
T: high
LH: low
in androgen insensitivity syndrome, Testosterone will be […], and LH will be […]
T: high
LH: high
[…] deficiency results in the inability to convert testosterone to DHT
5a reductase
form of hypogonadotropic hypogonadism that cause inability to complete puberty
Kallmann syndrome
conversion of testosterone to DHT requires what enzyme
5a-reductase
aromatization of testosterone to estrogen requires what enzyme?
CYP19/aromatase
plays important roles in the development of prostate, skin, and hair follicles
DHT
plays important role in maintaining bone health, fat mass, and epiphyseal fusion
estrogen
DHT and T signal through […] receptor
androgen (AR)
estrogens signal through the […] receptors
estrogen (ESR1, ESR2, GPER)
androgen production […] with age
declines (andropause)
visual symptoms in the setting of hypogonadism may suggest
prolactinoma
(impinging on optic chiasm)
describe T, LH, and FSH in hypogonadotrophic hypogonadism
T low
LH: low
FSH: low
problem at level of pituitary
how does exercise induced hypogonadism cause HH?
reduced leptin –> reduced GnRH release
defective migration of neurons and subsequent failure of olfactory bulbs to develop
Kallmann syndrome
hCG is homologous to […] but with longer half life
LH
(can be used as LH analog for hormone therapy)
treatment for Klinefelter’s
testosterone if low
nothing if T is normal
in hypogonadotrophic hypoganadism, what will FSH and LH levels be?
both low
Kallmann’s syndrome is a type of […]gonadotrophic hypogonadism
hypo
cystic fibrosis is accompanied with agenesis of
vas deferens
how long does a spermatogenesis cycle take?
about 3 months
what should be done to preserve male fertility prior to radiation therapy?
cryopreservation of sperm
[IVF/ICSI]
requires only one spermatazoon
ICSI
[IVF/ICSI]
requires a higher number of sperm
IVF
[IVF/ICSI]
sperm is injected directly into the egg
ICSI
(doesn’t have to be motile)
[IVF/ICSI]
requires that sperm is motile
IVF
[IVF/ICSI]
followed by embryo transfer to mother
both
causes of retrograde ejaculation [3]
diabetes
medications to relax bladder sphinter
spinal cord injury
(things that would affect control of the bladder sphincter)
what test will confirm a diagnosis of retrograde ejaculation?
analysis of sperm in urine
agglutination of sperm indicates
autoimmunity
(presence of anti-sperm antibodies)
changes to volume/composition of sperm indicates
obstruction of genital tract
what would you expect on semen analysis of a patient with retrograde ejaculation?
aspermia
what would you expect on semen analysis of a patient with history of parotiditis (mumps)?
azoospermia or oligospermia
most common complications of varicocelectomy [2]
orchitis
hydrocele
couples are advised to have […] before radiotherapy is performed
sperm retrieval
a semen specimen that is missing fructose indicates
absence of seminal vesicles
what would you expect levels of inhibin, LH and FSH to be in a patient taking exogenous steroids?
all low
asthenozoospermia is defined as a total sperm motility less than […]% and progressive motility less than […]%
asthenozoospermia is defined as a total sperm motility less than 40% and progressive motility less than 32%
genetic disease in which cilia and flagellum are altered
Kartageners
characterized by dextrocardia, bronchitis, disosmia, and infertility
Kartageners
cause of azoospermia due to undescended testes
increase in temperature of testes affects spermatogenesis
what will LH, FSH, and inhibin levels be in a patient who is taking exogenous steroids?
all low
what would a semen analysis show following a successful vasectomy?
azoospermia
(ejaculate without sperm)
hCG can be prescribed to males to treat
congenital cryptorchidism
(binds to LH receptor on Leydig cells to stimulate leydig insulin-like hormone release, which triggers testicular descent)
defect in androgen receptor that is unlikely to be aided by exogenous androgens
androgen insensitivity syndrome
describe inhibin, LH, FSH, and T levels in Klinefelters
LH high
FSH high
T low
inhibin low
(due to testicular failure)
describe LH, FSH, and T levels in Kallmann syndrome
FSH low
LH low
T low
(due to failure for hypothalamus to stimulate testicles)
symptoms of sexual dysfunction [3]
decreased thoughts about sex
erectile dysfunction
sex frequency
(need to have these to indicate testosterone therapy)
once low T has been confirmed, what other labs should be assessed prior to starting testosterone therapy?
baseline PSA
baseline hematocrit
LH
FSH
if LH levels were found to be low in a man who had low T levels with normal sex characteristics, then […] should be screened
prolactin
