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71 Cards in this Set

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  • Back
Structure of testosterone(T) ?
4 rings like all steroids.
Not androgenic
Where is T made?
Leydig(interstitial) cells of testis and in ovary from cholesterol.
T is metabolized into DHT by
5 alpha reductase in target tissues.(prostae,hair follicles,genitals)
DHT potency is > than T in some tissues.
What regulates T synthesis?
LH from pituitary.
DHEA and androstenedione are?
Very weak adrenal androgens
To go bald,
you need DHT.
Drugs that block 5 alpha reductase are used to
treat prostate cancer/baldness.
What are the androgens?
Where are the above produced/
Androgenic effects ?
-Control sexual diff. in male
-Regulate function in male reproduction.
Anabolic effects ?
Promote growth of bone,muscle,prostate,other tissues.
Main androgen
Main function of T
-masculinising function
-growth promoting function.
--> regulate reproduction in males.((expressed in utero,neonatal periods,puberty)
T actions ?
-sexual diff. of internal/external genitalia in utero
-adult life:role in testis and role outside testis.
How many phases of androgen activity?
What are the 3 main periods when pituitary gonadal axis is active?
-midtrimester of fetal period
-during early neonatal period
-from puberty throughout reproductive years.
-switches on the Y chromosome
-testis determining factor on Y chrm.
Being female is
Default state.
If SRY is active,
Dev. gonad becomes a testis.
What does testis secrete?
-AMH(anti mullerian hormone) or MIS
What are the 2 duct systems present in embryo?
-Wolfian duct has potential to develop into male genital tract.
-Mullerian duct has potential to dev. into female genital tract.
Y chrm w/o SRY ?
XY female
Y chrm translocated onto X chrm ?
XX male
T initiates dev. of ?
Male internal genitals(epididymis,vas deferens,seminal vesicles)
DHT is required for ?
Dev. of external male genitalia and prostate(prostate,urethra,penis,scrotum)
AMS(MIH) causes ?
regression of mullerian duct which otherwise dev. into--> fallopian tubes,uterus & upper third of vagina.
What are the 2 types of cells from testis ?
Sertoli cells produce
Leydig cells produce
T + AR gives
-Wolfian duct dev.
-Masculinization of internal organs
-Maintenance of spermatogenesis.
DHT + AR gives ?
-masculinization of external genitalia
-Dev. of prostate
-Dev. of secondary sexual characteristics.
T actions during puberty?
-Penis and testis enlarge
-Growth of facial hair
-Increased sebum production
-Pubic hair
-Growth in height and increase in muscle size
-vocal cords enlarge and larynx enlarge.
High conc. of T are present in testis
True-required for spermatogenesis.
Role of T outside testis ?
-Bone/muscle strength
-hair growth and baldness
-psycho function.
-aging ?
XY baby with no androgen Receptor cannot dev. neither external nor internal genitali but testis working-->T not acting but MIH still produced with atrophy of vagina and uterus BUT still dev. like normal females at puberty.why ?
Excess T metabolized to estrogen by aromatase at puberty.
In human males,hormonal activity is only 1 factor of sexual behaviour.
Seminal vesicle atrophies w/o T.
not enough T in males.
T actions in females
-Pubic and axillary hair
-bone strength
-muscle strength(works better in females)
-Sexual function-libido
-Psychological function
What happens when T levels increase in women?
-breasts atrophy
-Increase in size of genitals
What can this be a sign of ?
-Testicular secreting tumour of ovaries
Dx of females pt with frontal baldness,deep voice,hirsutism,enlarged clitoris.
ovarian tumour.
Diff. between the various steroid hormone receptor superfamily lies in
Diff. ligand binding domains.
T action is via ?
Protein synthesis.
Androgen responsive systems?
on almost all tissues of body.
Androgen responsive systems in the erythropoietic system causes
Increase in RBC
Androgen responsive systems in reproductive/sex tissues responsible for ?
-Genital dev.
-Prostate dev.
-Breast (-VE)
Androgen responsive systems in brain/nervous system responsible for ?
-Behavioural modulation
-motor neurones(KENNEDY's disease)
What are the simple Androgen response elements ?
-Consensus GRE
What are some complex AR binding sites?
-multiple weak AREs
-non consensus binding sites.
Androgen responsive genes
regulate many genes:-
-growth factors
-secretory factors
-matrix/structural pz.
Pituitary or testicular disease of T metabolism causes ?
-Delayed puberty
-Hypogonadism in adults.
Hypogonadism in adult males ?
-Decreased libido
-Decreased muscle bulk
-Osteoporotic fractures
-Changes in personality
--> can be reversed by T replacement.
Defects in 5 alpha reductase(T-->DHT) leads to
-females external genitals at birth in XY pts
-masculinise at puberty
We need DHT for
External genitalia dev.
XY females can have
What is Androgen insensitivity(AIS) ?
Loss of function mutations in the androgen receptor.(genetic defect in T action)
-XY females
-male T levels
-female external genitalia
-no uterus nor fallopian tubes
-breasts at puberty
In New Guinea,pts born females and masculinize at puberty.why?
Increased levels of T and 5 alpha reductase at puberty.
AR gene mutations cause loss of function in
AIS(partial or complete)
AR gene mutations cause GAIN in function in
-prostate cancer(increased hormone responsiveness)
-Kennedy's disease
-Breasts cancer.
Kennedy's disease ?
-motor neuron disease
-Spino-bulbar muscular atrophy
-Trinucleotide repeat expansion in exon A
-> 40 triplets
-Increased length of Gln in Amino terminal domain
-Decreased transactivation
Prostate cancer ?
-AR mutations at specific sites in ligand binding domain
-Mutations in primary and secondary cancers
-receptor activation by adrenal androgens,anti-androgens & estrogens.
Clinical uses of T ?
-Replacement if inadequate production(pituitary disease/testicular disease)
-Contraception(doesnt work orally)
-Body building(illicit in sport)
T is synthetized by
testis and to small extent by ovary.
T is converted locally to more potent DHT in
T regulates :-
-Sexual diff
T is required for
Dev of male internal genitalia
DHT required for
Dev. of prostate and external male genitalia.
Androgens act by
Binding to INTRAcR receptors which regulate gene expression.