Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
57 Cards in this Set
- Front
- Back
|
What hormone is highly conserved among species?
|
GnRH
|
|
|
What 2 hormones are co-secreted from GnRH neurons?
|
GnRH and GAP?
|
|
|
What is the half life of GnRH?
|
Short, <10min
|
|
|
What clinical relevance does the short half life of GnRH have?
|
Serum levels are too low to dectect --> measure LH instead
|
|
|
What are the 2 output profiles of GnRH in men?
|
1. Circadian - most frequent in Am
2. Pulsatile - every 90-120 minutes |
|
|
When is the best time to obtain T levels?
|
Before 10am because that is when they will be the highest (therefore can detect a deficiency)
|
|
|
What kind of receptor is the GnRH receptor?
|
GPCR
|
|
|
What 3 things occur in the pituitary in response to GnRH?
|
1. Exocytosis of LH and FSH
2. Increased synthesis of LH and FSH 3. GnRH receptors are then internalized |
|
|
If GnRH pusles become too frequent or is continuous, what occurs?
|
GnRH receptor down-regulation with resulting low LH/FSH level
|
|
|
What is the half life of LH?
|
Short (20 min)
|
|
|
The short half life of LH is due to what?
|
Quick cleavage by the liver enzymes that recognize the sulfate residues
|
|
|
In males, how often are pulses of LH seen?
|
Every two hours
|
|
|
What is the half life of FSH?
|
Long (2 hours) - so serum levels remain steady
|
|
|
FSH mirrors what?
|
Spermatogensis - stimulates sertoli cells to support spermatogenesis
BUT not fully 100% necessary |
|
|
LH stimulates what cells?
|
leydig cells to produce testosterone
|
|
|
What is the negative feedback to the hypothalmus to decrease GnRH pulsation?
|
Testosterone and DHT
|
|
|
What is the negative feedback in the pituitary?
|
E2 modifies GnRH response by reducing LH and FSH pulse AMPLITUDE
|
|
|
Initially in the male fetus, what controls the development of the testes and male internal duct work?
|
Placental hCG
|
|
|
In infancy, what is seen in terms of GnRH and Lh/FSH secretion?
|
Very low levels prior to puberty
|
|
|
What happens in terms of hormones around puberty?
|
nocturnal FSH and LH pulses begin, then lasting throughout the day
HPG axis resets its sensitivity |
|
|
What is made in the testis in response to FSH and goes back to pituitary to cause negative feedback?
|
Inhibin B
|
|
|
What are the 2 main functions of the testis?
|
1. Steroidogenesis
2. Spermatogenesis |
|
|
What are the 2 types of compartmentalization seen in the testis?
|
1. Functional - different cell types respond to different signals and produce different hormones
2. Structural - physical isolation of haploid germ cells from immune recognition |
|
|
Where are Leydig cells found?
|
In the Interstitium, in close contact with circulation
|
|
|
What protein is important in the rate limiting step in testosterone production in leydig cells?
|
The STAR protein - transports cholesterol across inner mitochondrial membrane
|
|
|
What % of testosterone in free in circulation?
|
2%
|
|
|
To what 2 proteins does testosterone bind to in the blood?
|
1. SHBG
2. Albumin |
|
|
What could give a false positive testosterone deficiency test?
|
If there was a low amount of SHBG and/or albumin
|
|
|
What is a very important physical characteristic of the Androgen Receptor?
|
AR has 2 zinc-finger DNA binding domains
|
|
|
What can cause Androgen Insensitivity Syndrome?
|
Not having both Zing finger domaines
|
|
|
What cells secrete Inhibin B?
|
Sertoli Cells
|
|
|
During puberty, what is the SC's response to FSH and androgens?
|
Become mitotically active
|
|
|
In adulthood, are SC's mitotically active?
|
NO, mitosis halts with the beginning of meiosis in germ cells
|
|
|
How are SC's involved in the blood-testis barrier?
|
Occluding tight junctions form between SC's
|
|
|
When does the formation of the blood testis occur?
|
Coincides with prophase I of meiosis I
|
|
|
Breach of the BTB results in what?
|
Formation of anti-sperm antibodies (ie testicular torsion)
|
|
|
Why does the taking of exogenous T cause infertility?
|
Because does not enter the testis, but DOES cause negative feedback in pituitary to decrease LH/FSH production
|
|
|
What are the 4 ways that SC's support spermatogenesis?
|
1. Create special microenvironemnt
2. Exposing GC's to high T levels 3. Coordinate maturation via gap junctions between SC's and GC's 4. Transport different GC's toward the lumen |
|
|
What are the stem cells lining the seminiferous tubules that give rise to GC's?
|
Spermatogonia
|
|
|
What are the 2 types of spermatogonia?
|
1. Type A - do not divide
2. Type B - Divide, enters spermatogensis |
|
|
What are the characteristics of a primary spermatocytes?
|
MI, 2 pairs of homologous chromosomes
4 sister chromatids --> tetraploid |
|
|
What are the characteristics of a secondary spermatocyte?
|
MII, homologous chromosomes separate leaving 2 sister chromatids
|
|
|
What are the characteristics of spermatids?
|
Meiosis has ended already, sister chromatids separate --> haploid (23N)
|
|
|
What are the 4 basic stages of spermiogenesis?
|
1. Golgi - acrosomal bubbles
2. Cap - nucleus condenses; all transcription stops 3. Acrosome - acrosome becomes prominent 4. Maturation - extrusion of cytoplasm as residual body |
|
|
How do the stages of spermatogenesis appear to progress around the seminiferous tubules?
|
appear to progress in a helical fashion
|
|
|
How long does a complete cycle of spermatogenesis take to complete?
|
64 days
|
|
|
What hormone regulates spermatogenesis?
|
Testosterone
|
|
|
What causes primary hypogonadism?
|
Testicular Defect
|
|
|
What causes secondary hypogonadism?
|
Central defect (ex: hypothalamic GnRH secretion or pituitary gonadotropin secretion)
|
|
|
What abnormal hormone levels are seen in "isolated spermatogenic failure"?
|
elevated FSH
|
|
|
What are the abnormal hormonal levels seen in hypergonadotropic hypogonadism (testicular failure)?
|
Elevated FSH and LH
Low T |
|
|
What are the abnormal hormonal levels seen in hypogonadotropic hypogonadism?
|
Low FSH/LH/T
|
|
|
What is one syndome that causes male infertility?
|
Klinefeter Syndrome (47XXY)
|
|
|
What are specific gene regions that have been implicated in low sperm production?
|
Y chromosome microdeletions in AZF regions localized to long arm of Y chromosome
|
|
|
AZFa is associated with what?
|
Uniform azoospermia, sertoli cells only
|
|
|
AZFb is associated with what?
|
Immature sperm development
|
|
|
AZFc is associated with what?
|
can retrieve 75% of time by mTESE and may even exhibit oligozoospermia
|
