Male Physiology Flashcards
Male reproductive hormones and where they come from
hypothalamus: GnRH
ant pituitary: FSH and LH
testes: inhibin b and testosterone
FSH function
acts on Sertoli cells
promotes Sertoli function (spermatogenesis)
Sertoli secrete inhibin b
inhibin b is negative feedback to prevent further FSH secretion from pituitary (but no feedback to GnRH)
LH function
acts on Leydig cells
promotes Leydig function (testosterone release)
testosterone acts on many body tissues
testosterone feeds back onto BOTH hypothalamic GnRH and pituitary LH
How does an increase in testosterone above normal levels possibly cause infertility?
testosterone feeds back onto hypothalamic GnRH
prevents downstream release of FSH
less stimulation of Sertoli cells
Which loop FSH/LH has long feedback loop onto hypothalamus
testosterone feeds back all the way to hypothalamus (and ant pituitary ie LH release)
inhibin b from Sertoli cells only feeds back onto FSH release from ant hypothalamus
How long does it take for sperm to get from little baby sperm all the way to mature sperm?
2 months
this is important because toxic exposure can decrease sperm production for up to 2 months until new sperm are produced
Why are sperm not destroyed by the man’s immune system?
Sertoli cells create a blood-testes barrier
Sertoli cells make men men embryologically
how
Sertoli cells secrete Müllerian inhibiting substance
prevents from embryo remaining female
Spermatogenesis is sensitive to what hormone level
testosterone
Why does taking exogenous testosterone cause testicular atrophy
decreases GnRH and LH levels
testicles not stimulated to produce testosterone
tissue isn’t needed to it atrophies
Inhibin b is produced by
Sertoli cells
in response to FSH
Testosterone is produced by
Leydig cells
in response to LH
Testosterone is anabolic/catabolic
anabolic
promotes protein synthesis and muscle growth
How does testosterone affect bones
testosterone promotes closure of epiphyseal plates
How to test for hypotestosteronemia
> 1 low testosterone value
==> follow up with FSH/LH levels
*really LH is the one that matters
How is testosterone transported in the blood
on SHBG (sex hormone binding globulin)
The testosterone receptor is what type of receptor
nuclear receptor
creates homodimer
GnRH receptor
Gq receptor (queer) activates PKC
Why are oral androgens hard to do?
first pass metabolism
Methyl-testosterone
MOA
Tox
MOA: testosterone replacement
Tox: hepatotoxic
Oxandrolone
MOA
TU
Tox
MOA: DHT derivative, cannot be converted w/ aromatase
TU: muscle growth
Tox: decreased risk of hepatotox compared to methyltestosterone
Flutamide
MOA
TU
Tox
MOA: antagonist at androgen receptor
TU: prostate ca
Tox: gynecomastia, hepatotox
Bicalcutamide
MOA
TU
Tox
MOA: antagonist at androgen receptor
TU: prostate ca
Tox: gynecomastia, hepatotox
Nilutamide
MOA
TU
Tox
MOA: antagonist at androgen receptor
TU: prostate ca
Tox: gynecomastia, hepatotox
