Q2: sex hormones Flashcards
which cells secrete testosterone/produce sperm
leydig vells; secrete testosterone (interstitial cells)
seminiferous tubules produce sperm (they are the bulk of testis)
what 3 hormones are involved in male reproductive function
testosterone , dihydrotestosterone (more potent than testosterone) , estradiol
what what 2 hormones of the testes have no known role in male reproductive function
dehydroepiandrosterone (DHEA) and androsternedione
what are the effects of testosterone
- masculinizes reproductive tract/external genitalia.
- promotes descent of testes into scrotum
- promotes growth and maturation of reproductive system at puberty
- essential for spermatogenesis
- maintains reproductive tract throughout adulthood
- develops sex drive at puberty
- gonadotropin hormone secretion control (include fsh and lh)
secnodary: hair, voice, muscles
what are the nonreproductive actions of testosterone
- protein anabolic effect
- bone growth at puberty
- clooses epiphyseal plates after being converted to estrogen by aromatase
- aggressiveness
when are there spikes in testosterome throughout life
spike after fertilization and drop. then another spike before the first year of age. then testosterone is low until puberty. This increase in testosterone induces sperm production.
-drop in senior years
what is SRY
sex determining region of the Y chromosome
what are the destinations of testosterone (pathway from production to target cells)
it may enter seminiferous tubules (from leydig, site of production) and induce sperm production. some also enters into circulation. in blood 98% travels bound to serum proteins and only 2% is free.
- at target cells binds to ANDROGEN RECEPTORS>
- location on membrane, cytoplasm or bone depends on cell for the androgen receptors. testosterone androgen receptor complex either activates cell signaling pathway (nongenomic) or gene transcription (genomic)
describe function of GnRh and its feedback inhibition
hypothalamus releases gonadotropin releasing hormone (GnRh) into anterior pituitary. it stimulates secretion of follicle stimulating hormone (FSH) and luteinizing hormone (LH) from gonadotropic cells
-feedback inhibition; sex hormones inhibits Kiss1 neurons from secreting kisspeptin. (kiss peptin stimulates GnRH release) – neg feedback
what does FSH / LH do?
FSH stimulates sertoli cells (sustentocytes) to release androgen binding protein (ABP)
-abp keeps concentration of testosterone in spermatogenic cells high, stimulates spermatogenesis
LH stimulates testosterone secretion in leydig cells
how is testosterone regulated ?
function of inhibin and kiss1neurons
inhibiition of kiss1 neurons when theres a lot of testosterone (kisseptin stimulates gnrh release)
-lots of testosterone inhibits release of LH from anterior pituitary
INHIBIN: protein hormone from sertoli cells, regulates spermatogneeis. high sperm count stimulates inhibin release, it inhibits release of FSH from anterior pituitary
what is estradiol
most active estrogen
estrogen= from ovaries
when is progesterone produced (which phase) in large amounts
luteal phase
where are estrogen and progesterone made?
synthesized and released by granulosa cells, no storage of the hormones
what % of estradiol is free, sex hormone binding globulin (SHBG), corticosteroid binding globulin (CBG) and albumin bound?
free: 2%
SHBG: 37%
CBG : .1%
albumin: 61%
WHAT % OF PROGESTERONE IS FREE, SHBG, CBG, ALBUMIN bound?
free: 2.5%
SHBG: .5%
CBG: 18%
albumin : 79%
what % of testosterone is free, bound to SHBG, CBG, albumin?
free: 1.5%
SHBG: 66%
CBG: 2.5%
albumin: 30%
what are the functions of estrogen
- ova maturation/release
- development of physical characteristics
- transport of sperm from vagina to egg
- development of breast in anticipation of lactation
- fat deposition
- bone density increase
- close epiphyseal plates
- improves blood cholesterole by increasing HDL and decreasing LDL
- promotes vasodilation by increasing NO production in arterioles
what is the function of progesteron
- prepare suitable environment for nourishing developing embryo
- contributes to milk production
what are the 2 phases of the ovarian cyclw
follicular phase: presenece of maturing follicles
luteal phase: corpus luteum (progesterone)
-corpus luteum secretes hormones to prepare female reproductive tract for pregnancy. in case releaserd egg is ferilized. degeneration of corpus luteum signals end of luteal phase.
what are thecal cells
endocrine cells of ovarian follicles. in interfollicular stroma which enclose granulosa cells. the granulosa cell surrounds ovum and antrunm, which is at the center of the follicle.
LH stimulates theca cells to produce androgen.
androgen diffuses from thecal cells into granulosa cells.
fsh stimulates granulosa cells to convert androgen into estrogen.
-some estrogen are secreted into blood and induce systemic effects while the other portion fo estrogen remains within the follicle, and contributes to follicle maturation.
whats ovarian hyperandrogenism
high androgen is related to excessive proliferation of theca cells. (low= theca cell dysfunction)
describe hormones throughout entire follicular phase
follicular phase: fsh is higher than LH. FSH and LH stimulate oocyte development and follicle growth. the follicle produces estrogen. as estrogen levels increase, endometrium thickens…
- the rising estrogen inhibits FSH secretion from anterior pituitary. FSH levels are further decreased since the follicle releases inhibin (which decreases FSH too from AP).
- estrogen continuesto be produced and estrogen levels increase (gramulosa cells keep making it)
- since estrogen ONLY inhibts fsh, LH continues to increase
- both estrogen AND progesterone are needed to supress LH secretion (not just estrogen)
- estrogen levels hit a peak, at this point it stimulates kiss1neurons to release kisspeptin which induces hypothal to release GnRH, FSH and LH-> spike in both.
- fsh not as intense bc follicle is still releasing inhibit which only impacts fsh. estrogen levels start to decrease as granulosa cells reduce production.
- surge in LH triggers ovulation (ends follicular phase)
how does kiss1neurons impact female ovarian cycle
kisspeptin release, stimulates GnRH just like in men . gnrh stims release of LH and FSH. the kiss1 activity can be inhibited by rising levels of estrogen
