Sex Hormones (Dragatsis) Flashcards
all sec hormones are derived from
cholesterol
describe the synthesis of testosterone
cholesterol → pregnenolone → progesterone (via 3-beta HSD) → testosterone
describe the synthesis of estradiol
cholesterol → pregnenolone → progesterone (via 3-beta HSD) → testosterone → estradiol (via aromatase)
describe the synthesis of dihydrotestosterone
cholesterol → pregnenolone → progesterone (via 3-beta HSD) → testosterone → dihydrotestosterone (via 5alpha-reductase)
What is the optimal temp needed for spermatogeneisis?
<37 C (2 degrees less than body temp)
How is the optimal temp for spermatogenesis maintained?
- pampiniform plexus acts as a countercurrent heat exhanger for the blood as it enters the testes
- the testes can be moved via the cremaster muscle to bring them closer to the body when it is cold (↓ surface area)
- sweating
What are the male accessory sex glands?
bulbourethral glands
seminal vesicles
prostate
what is in the seminal vesicle fluid?
PGs, fructose, citric acid
semen =
sperm + secretions (from SV and prostate)
spermine
fluid in prostste
slightly alkaline, increases sperm motility and neutralizes acidic vagina
What are the primary male sex organs and secondary male sex organs?
primary = testes
secondary = epididymis, vas deferens, ejaculatory duct, urethra (and penis), accessory glands (bulbourethral glands, seminal vesicles, prostate )
What are secondary male sex characteristics?
changes observed (at the beginning of puberty) in hair growth, body shape, voice
Are all male pubertal changes are irreversible?
no, spermatogenesis, size, secretions and content can change/reverse to pre-pubertal stage
*voice and height do not change, libido, muscle mass and hair growth can slowly reverse
What hormones are required for spermatogenesis?
directly: FSH and T (at high conc)
indirectly: LH (to stim ↑↑ T) and GnRH (to stim ↑↑ LH and FSH)
site of action for FSH and T in males
sertoli cells
function of sertoli cells
- stimulate spermatogenesis
- nourish sperm
- protect sperm (provide barrier to many chemicals)
- make inhibin (negatively feedback on FSH production)
- secrete luminal fluid
- phagocytosis of dead or defective sperm
What are 2 notable products of sertoli cells
inhibin and ABP
what stimulates the production of testosterone
LH
secretion rhythm of testosterone
pulsitile (bc GnRH is and ∴ LH and ∴ T)
**note, realive to the changes of gonadotrophins in females over a month, LH, FSH, and T in males are RELATIVELY stable
In some target tissued T must be converted to _______ in order to reach the nucleus and produce androgenic effect
dihydrotestosterone (DHT)
What are the androgenic effects that are mediated by DHT
Fetal formation of prostate and external genitalia require what hormone
pubertal enlargement of prostate, hair changes, acne
What enzyme converts T to DHT
5alpha reductase
What sex hormone is predominantly secreted by the testes?
T
What sex hormone is secreted by the adrenals?
estradiol
What sex hormones are converted from precursors? Name the precursors
DHT (from T)
Estradiol (from T)
What are the androgenic effects that are mediated by T (i.e. does not need to be converted to DHT)
pubertal growth of skeletal muscle, penis, and scrotum
libido
Testosterone is metabolized by … and excreted in/as….
liver (glucuronated and sulfonated)
urine as 17-ketosteroids
What % of T is free in the blood
3%
What is T bound to in the blood?
70% to SHBG and 30% albumin
T reaches these cells via luminal fluid NOT blood
epididymis
**bound to ABP
What substance causes negatively feedback for LH?
Testosterone
What substance causes negatively feedback for FSH?
inhibin (secreted by sertoli cells)
acts on PITUITARY
*T does this weakly
Effect of T on the skin
predisposes to acne by stimulating production of thick secretion
stimulates pubic, axillay, and fascial hair growth
stimulates hair recession
negative feedback regulator od GnRF
T and estrogens
What effect do estrogens have on GnRH secretion
decrease the pulse frequency of release
It takes large amounts of androgens (T) to shut off ______ and cause the balls to shrink. Specifically what part of dude’s junk is shrinking when they OD on androgens
FSH
absent FSH causes the seminiferous tubules to shrink
How to male sex hormones change as they age?
↓T = there is less negative feedback so LH and FSH ↑; estrogen also ↑
In an old man, SGBH ↑ or ↓
↑ (less free T)
what are the primary and secondary female sex organs?
primary = ovaries
secondary = oviducts, uterus, vagina, accessory glands (mucous and mammary?
skipping the stages of the ovary/follicle
bc dr nutting covered it more in depth
estrogen is produced in the…
ovaries (specifically the follicles and especially the dominant follicle)
Again, skipping the menstrual cycle slide
bc dr nutting covered it more in depth
effects of low E on hypothalamus and pit
inhibits LF and FSH (GnRH inhibited too)
effects of high E on hypothalamus and pit
simulates (GnRH→) LH and FSH and leads to mud cycle LH surge that causes ovulation
**very high E is inhibitory and was ∴ used for BC but due to the whole breast cancer thing that was stopped
effect of low E and progesterone on hypothalamus and pit
inhibits LF and FSH (GnRH inhibited too)
*todays BC
Effects of estrogen on female “configuration” of the body
widens hips; increases fat and changes distribution
