Lecture 11: Androgens Flashcards
Testosterone
-most important andgrogen
-excreted by testis
Testosterone function
-bind androgen receptor
-alter rate of transcription
Testosterone synthesis
-8mg produced daily
-95% by leydig cells in testis
-5% by adrenal gland
Plasma levels of testosterone
-0.6 ug/dL in men
-0.3 women
circulating testosterone states
-bound to SHGB 65%
-bound to albumin 33%
-free 2%
Regulation of testosterone synthesis
-testosterone inhibits production of testosterone
-inhibits hypothalmus, anterior pituitary
Leydig cells
-produce testosterone from LH
setoli cells
-stimulated by FSH
Testosterone + aromatase
-17B-estradiol
testosterone + 5a reductase
-5a-dihydrotestosterone
5a-dihydrotestosterone
-more potent
-major active androgen
Testosterone excretion
-occurs in liver
-inactivated to androsterone or ethiocholanolone then conjugated
Adrenal androgens
-intermediates of testosterone synthesis
-produced in significant amts
-produced in adrenal glands
-weak androgen effects
-unknown physiological functions
Adrenal androgen examples
-androstenedione
-DHEA
-DHEAS
Testosterone effects
-puberty changes
-growth promotion
-stimulation and maintenance of sexual function
-stimulate erythrocyte production
-decrease HDL levels
growth-promoting properties of testosterone
-penile and scrotal growth
-thick and oily skin
-axillary hair
-deep voice
-skeletal growth
-increase lean body mass (positive N balance)
Clinical uses of testosterone
-male androgen replacement therapy
-gynecologic disorders
-protein anabolic agents
-andropause
androgen replacement therapy in men
-male hypogonadism (testosterone deficiency)
-hypopituitarism
gynecologic disorders treated by testosterone
-endometriosis
-in combo with estrogens for replacement therapy in postmenapausal women
-eliminates endometrial bleeding
-enhances libido
protein anabolic agents testosterone use
-reverse protein loss after trauma/immobilization
-in combo with diet and exercise
Synthetic androgens types
-17-alkyl forms (oral)
-ester forms (intramuscular)
17-alkyl synthetic androgens
-methyltestosterone
-active orally
ester synthetic androgens
-prolonged absorption
-better as IM injection
-propionate, enathate, cypionate
Anabolic steroid use in sports
-10-200 x larger than daily dose
-increase strength and aggressiveness
-effects only seen in women
-suppress secretion of gonadotropins = testicular atrophy
