W9- Lecture 47- Endocrine regulation of reproduction Flashcards
where is Gonadotrophin releasing hormone (GnRH) produced by ?
how is the flow of it ?
by median eminence of hypothalamus.
released in pulses
what happens when Gonadotrophin releasing hormone is released ?
diffuses to pituitary & causes release of gonadotropins
luteinising hormone (LH) & follicle stimulating hormone (FSH)
name two types of gonadotropins
luteinising hormone (LH) & follicle stimulating hormone (FSH)
what happens is Gonadotrophin releasing hormone overstimulates the pituitary gland ?
/ why
initial surge in gonadotrophins then
overstimulation with GnRH leads to gonadotropin depletion & deficiency.
as gonadotropin reserves are replenished between pulses
what is the function of FSH (Follicle Stimulating Hormone):
Acts on the Sertoli cells (only)
variety of effects, especially production of Androgen Binding Protein (ABP) for transport of testosterone around blood.
Also has a direct effect on germ cells (via the Sertoli cells)
what is the function of LH (Luteinising Hormone)
acts on the Leydig cells, which then produce testosterone (T).
T stimulates germ cells directly but also acts on bone, skin, hair and the accessory sexual organs (post-puberty).
T also converted to: dihydrotestosterone (DHT) – effects on prostate; and oestradiol – important in epiphysial closure and reproductive system.
describe the feedback system of FSH
+ location
negatively regulated by inhibin, produced by Sertoli cells
Also positively regulated by activin & follistatin
regulation happens at pituitary
describe the feedback system of LH
+ location
negatively regulated by T
regulation at both pituitary and hypothalamus.
what are the 4 stages of the ovarian cycle ?
+ time of each part of the cycle
which cycle has the greatest variability ?
follicular phase (10-16 days)
ovulatory phase (36 hours)
luteal phase 14 days
menstruation (4-5 days)
greatest variability: follicular phase
describe the quantity of FSH over the ovarian cycle
review graph
describe the quantity of LH over the ovarian cycle
review graph
human Chorionic Gonadotrophin (hCG) produced in an embryo is similar to what other hormone ?
Luteinising Hormone
describe the ovarian cycle regulation in terms of
- GONADOTROPHIN SYSTEM
- OVARIAN HORMONES
GONADOTROPHIN SYSTEM
hypothalamic control GnRH (LHRH)
LH and FSH; pulsatile release
OVARIAN HORMONES
2 main steroids- cyclical production
oestrogens (oestradiol)
progestogens (progesterone)
describe the hormonal control of Follicular Development
FSH acts on primary and secondary follicles
causes follicular growth
promotes oestradiol secretion from follicles
inhibin (peptide hormone from granulosa cells ) also secreted
oestradiol/inhibin causes negative feedback on FSH
FSH decreases as oestradiol rises
describe the hormonal control of Ovulatory Phase
By day 12 oestradiol achieves threshold to switch to positive feedback
surge of LH(compared to FSH)
oocyte matures
release of ovum (+ 36hr)
describe the hormonal control of the Luteal Phase
+ late luteal phase
Empty tertiary follicle collapses – residual granulosa cells luteinise & invade - endocrine structure - corpus luteum Secretes oestradiol and progesterone maintains endometrium progesterone suppresses LH/FSH
late Luteal phase
corpus luteum involutes (invaded by macrophages)
oestradiol and progesterone fall
endometrium not maintained (menstruation)
loss of negative feedback
FSH rises
what changes in the hormonal control if fertilisation occurs ?
ovum implants
uterus secretes chorionic gonadotrophin (hCG)
hCG maintains corpus luteum(no involuting )
corpus luteum secretes oestradiol and progesterone
endometrium maintained
no menstruation
pregnancy established
what are Effects of Oestrogens in both sexes ? other then control of menstrual cycle
maintenance of bone mass (both sexes) effects on CNS (both sexes) effects on vasculature (both sexes) effects on lipid metabolism effects on fat distribution promote insulin secretion effects on blood clotting (thrombosis)
what are the effects od progesterone
other then control of menstrual cycle
causes body temperature to rise
causes change to thick (non-receptive) cervical mucus secretion
down regulates oestrogen receptors
exerts a negative feedback control on the hypothalamus and pituitary
name some effects of menopause
caused by ?
Early 40’s – 50’s: climacteric, mood changes, loss of libido, hot flushes
Caused by decline in ovarian foll. no’s + reduced responsiveness to gonadotrophins.
Loss of oestrogen leads to
increase in LH + FSH.
name three effects of Vasomotor changes
are these a risk factor for any other problems ?
hot flushes, night sweats
reduction in vaginal lubrication
rise in pH lead to discomfort
increased risk of coronary thrombosis.
how can women going through menopause be treated for a Increased risk of osteoporosis ?
HORMONE REPLACEMENT THERAPY
