W9- Lecture 47- Endocrine regulation of reproduction

Question 1

where is Gonadotrophin releasing hormone (GnRH) produced by ?
how is the flow of it ?

Answer 1

by median eminence of hypothalamus.

released in pulses

Question 2

what happens when Gonadotrophin releasing hormone is released ?

Answer 2

diffuses to pituitary & causes release of gonadotropins

luteinising hormone (LH) & follicle stimulating hormone (FSH)

Question 3

name two types of gonadotropins

Answer 3

luteinising hormone (LH) & follicle stimulating hormone (FSH)

Question 4

what happens is Gonadotrophin releasing hormone overstimulates the pituitary gland ?
/ why

Answer 4

initial surge in gonadotrophins then
overstimulation with GnRH leads to gonadotropin depletion & deficiency.

as gonadotropin reserves are replenished between pulses

Question 5

what is the function of FSH (Follicle Stimulating Hormone):

Answer 5

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)

Question 6

what is the function of LH (Luteinising Hormone)

Answer 6

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.

Question 7

describe the feedback system of FSH

+ location

Answer 7

negatively regulated by inhibin, produced by Sertoli cells
Also positively regulated by activin & follistatin
regulation happens at pituitary

Question 8

describe the feedback system of LH

+ location

Answer 8

negatively regulated by T

regulation at both pituitary and hypothalamus.

Question 9

what are the 4 stages of the ovarian cycle ?
+ time of each part of the cycle

which cycle has the greatest variability ?

Answer 9

follicular phase (10-16 days)
ovulatory phase (36 hours)
luteal phase 14 days
menstruation (4-5 days)

greatest variability: follicular phase

Question 10

describe the quantity of FSH over the ovarian cycle

Answer 10

review graph

Question 11

describe the quantity of LH over the ovarian cycle

Answer 11

review graph

Question 12

human Chorionic Gonadotrophin (hCG) produced in an embryo is similar to what other hormone ?

Answer 12

Luteinising Hormone

Question 13

describe the ovarian cycle regulation in terms of

1. GONADOTROPHIN SYSTEM
2. OVARIAN HORMONES

Answer 13

GONADOTROPHIN SYSTEM
hypothalamic control GnRH (LHRH)
LH and FSH; pulsatile release

OVARIAN HORMONES
2 main steroids- cyclical production
oestrogens (oestradiol)
progestogens (progesterone)

Question 14

describe the hormonal control of Follicular Development

Answer 14

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

Question 15

describe the hormonal control of Ovulatory Phase

Answer 15

By day 12 oestradiol achieves threshold to switch to positive feedback
surge of LH(compared to FSH)
oocyte matures
release of ovum (+ 36hr)

Question 16

describe the hormonal control of the Luteal Phase

+ late luteal phase

Answer 16

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

Question 17

what changes in the hormonal control if fertilisation occurs ?

Answer 17

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

Question 18

what are Effects of Oestrogens in both sexes ? other then control of menstrual cycle

Answer 18

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)

Question 19

what are the effects od progesterone

other then control of menstrual cycle

Answer 19

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

Question 20

name some effects of menopause

caused by ?

Answer 20

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.

Question 21

name three effects of Vasomotor changes

are these a risk factor for any other problems ?

Answer 21

hot flushes, night sweats
reduction in vaginal lubrication
rise in pH lead to discomfort

increased risk of coronary thrombosis.

Question 22

how can women going through menopause be treated for a Increased risk of osteoporosis ?

Answer 22

HORMONE REPLACEMENT THERAPY