Sex hormones Flashcards
Testosterone actions
Stimulates enlargement of testes and male accessory organs
Stimulates development of male secondary sex characteristics
Suppresses FSH and LH secretion and GnRH production
Metabolism of testosterone
by 5-alpha reductase to active metabolite dihydrotestosterone (DHT)
Dihydrotestosterone (DHT)
causes development of male external genitalia
by binding to cytoplasmic androgen receptors
Leydig cells of testes
activated by LH and secrete testosterone
Sertoli cells
activated by FSH
secrete anti-mullerian hormone and androgen binding protein (ABP)
Anti-mullerian hormone (AMH) function
causes regression of mullerian duct
Androgens made within adrenal cortex
testosterone, androstenedione and dehydroepiandrosterone (DHEA)
Dehydroepiandrosterone (DHEA) function
causes early development of pubic/body hair in boys and girls
testosterone release process
- testes release testosterone
- 5-alpha reductase convert testosterone to DHT
- DHT binds to androgen receptor which releases heat shock proteins (hsp)
- hsp migrate to nucleus and bind to specific regions of DNA that contain Androgen Response Elements (ARE)
- ARE drive expression of genes that increase: growth, survival and PSA production
sex hormones secreted by pituitary gland
LH and FSH
hormone released by hypothalamus
GnRH (gonadotropin releasing hormone)
role of GnRH
stimulation of LH and FSH secretion
role of FSH and LH
stimulate gamete production in the gonads
how many sperm cells does 1 germ cell (spermatogonium) produce
1 germ cell = 1 primary spermatocyte = 2 secondary spermatocytes = 4 sperm cells
what is the product of Sex-determining region of Y chromosome (SRY gene)
testis-determining factor
male development at 10-week old foetus
- SRY protein in male embryo detects medulla of biopotential gonad to develop into testes
- Anti-Mullerian hormone from testis causes the mullerian ducts to diappear
male development at birth
- testosterone from testis converts Wolffian duct into seminal vesicle, vas deferens and epididymis
(DHT control prostate development)
what happens to gonad (cortex) in male and female development
M - regresses
F - forms ovary
what happens to Gonad (medulla) in male and female development
M - forms testis
F - regresses
what happens to Gonad (medulla) in male and female development
M - forms testis
F - regresses
what happens to Gonad (medulla) in male and female development
M - forms testis
F - regresses
what happens to Gonad (medulla) in male and female development
M - forms testis
F - regresses
what happens to Wolffian duct in male and female development
M - forms epididymis, vas deferens and seminal vesicle (testosterone present)
F - regresses (testosterone absent)
what happens to Mullerian duct in male and female development
M - regresses (AMH present)
F - forms fallopian tubes, uterus, cervix and upper half of vagina (AMH absent)
What do primary testicular failure (M) and hypogonadotropic hypogonadism (M+F)
infertility and associated hypogonadism and lack of 2nd sexual characteristics
Ovarian steroid hormones
- estrogens C18
- progestagens C21
- Androgens C19
how many egg cells does 1 germ cell (oogonium) produce
1 germ cell = 1 primary oocyte = 1 secondary oocyte (egg cell) = 1 egg cell released from ovary at ovulation
female development at 10 weeks (foetus)
- Gonadal cortex becomes ovary in absence of SRY protein and under influence of female-specific gene
- absence of testosterone causes Wolffian duct to degenerate
Female development at birth
- absence of anti-mullerian hormone allows Mullerian duct to become fallopian tubes, upper half of vagina, uterus
Role of estrogen
- maturation of germ cells
- anabolic effects on bone and cartilage (osteoporosis)
- maintenance of pregnancy
- growth development metabolism and reproduction
- labour and lactation
- development of tissue that will allow for implantation of blastocysts
- development and regulation of female reproductive system and secondary sex characteristics
increased progesterone effect in women
thickening of uterine wall
increased inhibin effect in women
LH and FSH inhibition
increased estrogen effect in women
release of inhibin
inhibition of FSH
physiological stages of fertilisation
- sperm cell fertilises ovum
- divides into 2 then 4 cells (blastocysts)
- blastocyst attaches itself to uterine wall (6-7 days)
- implantation of blastocyst in endometrium (11/12 days)
= embryo at 4 weeks
role of Human Chorionic Gonadotropin (hCG)
hormone detected in pregnancy tests
prevents degeneration of corpus luteum = continued secretion of estrogen and progesterone
role of estrogen in pregnancy
inhibits FSH and LH = no subsequent ovulation
role of progesterone in pregnancy
maintains integrity of uterine wall
placental hormones
Placental lactogen (hPL) hCG progestins lutenising hormone (LH) estrogens
labour related drugs
oxytocin
selective beta2 adrenergic receptor antagonist = prevents smooth muscle contraction
hormones involved with lactation
E2 - ductal growth
progesterone - inhibits milk production and secretion in late pregnancy
prolactin
oxytocin - stimulated by estrogens and inhibited by progesterone
physiology of menopause
increased LH and FSH - compensates decreased estrogen
ovaries fail to respond to FSH - number of remaining follicles decreases
physiological signs of menopause
decreased estrogen production
decreased testosterone
thinner vaginal walls
hormonal control of early to mid-follicular phase of menstrual cycle
- low level estrogen = -ve feedback to GnRH, FSH and LH
- increased estrogen secretion by follicle
- granulosa cells secrete AMH = prevents more follicles developing
hormonal control of late follicular phase and ovulation of menstrual cycle
- increased estrogen and progesterone = LH surge (important for ovulation)
- FSH suppressed by inhibin
hormonal control of early to mid-luteal phase of menstrual cycle
- increased inhibin, estrogen and progesterone = FSH and LH inhibition
hormonal control of late luteal phase of menstrual cycle
- decreased estrogen and progesterone when corpus luteum dies
- gonadotropins start follicular development for a new cycle
4 stages of menstrual cycle
- early to mid-follicular phase
- late follicular phase and ovulation
- early to mid-luteal phase
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