sex steroids Flashcards
SRY gene
testis determining factor
transcription factor that determines dev. of male gonad tissues
only on the y chromosome
female vs male gametes
XX
XY
what hormones are synthesised by testes vs ovaries?
testes: testosterone
ovaries: estrogen, progesterone
site of sex steroid production & common precursor
gonads, cholesterol
nature of sex steroids and why?
lipophilic, can go through any membrane
what is aromatase critical for?
determining whether androgen or oestrogen is primary active factor
aro = oestrogen produced
synthesis pathway for sex steroids
cholesterol - progesterone - testosterone
1. estrogen (via aro)
2. 5a-dihydrotestosterone (via 5a reductase)
male steroid synthesis over time
transient - peak at puberty - constant in adult
female steroid synthesis over time
low - puberty increase - cyclic over adulthood - decrease at menopause
what is sex steroid synthesis regulated by?
FSH & LH released by pituitary gland (reg. by hypothalamus)
sexual dimorphism
how?
permanent differences between sexes (anatomical, physiological, behavioural)
1. expression of aromatase & different hormone receptors
2. sex specific neurons
speed of steroid action on cells (and why)
slow onset and offset
(bc proteins have to become expressed)
hours - days
estrogen as critical masculinising factor
(in neurons that express aro)
inc. T = inc. E
E acts on ERs in these neurons, influencing properties
this is LOCAL
a-fetoprotein function
fetus protected by a-fetoprotein
binds circulating estrogens, doesn’t change fetus brain by circulating hormones
steroid receptor independent effects
RAPID effects directly modulate other signalling pathways, second messengers, ion channels
SLOW long effects affect gene expression
