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Reproduction > Reproductive Endocrinology in Small Animals > Flashcards

Reproductive Endocrinology in Small Animals Flashcards

1
Q

What are the secretory products of the:

  1. Follicular phase
  2. Luteal phase
A
  1. Oestrogen dominant (E2)

2. Progesterone dominant

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2
Q

How is the oestrus cycle classified in terms of vaginal cytology?

A

Pro-oestrus: rise in oestrodiol
Oestrus: maximum oestrodiol
Metoestrus: transitional
Dioestrus: progesterone dominant

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3
Q

How can the reproductive physiology of the bitch and queen be described?

A 
Bitch:
Mono-oestrus
Non-seasonal
Polytocous
Spontaneous ovulation

Queen:
Seasonally polyoestrus
Polytocous
Induced ovulator

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4
Q
  1. When does the bitch ovulate?
  2. What is follicular development regulated by?
  3. What is LH and FSH secretion regulated by?
A
  1. Ovulates spontaneously at end of variable follicular phase (4-28d)
  2. FSH and LH, which acts to synthesis oestradiol
  3. GnRH from the hypothalamus and steroids from the ovaries
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5
Q

What are the stages of the canine oestrus cycle?

A

Proestrus (9days)
Estrus (9days)
Pregnancy/Diestrus (60days)
Anestrus (>90days)

Estrus = receptive to mating efforts of male

Pregnancy = lasts as long as luteal phase (difficult to diagnose because clinical signs similar to luteal phase)

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6
Q

Describe how LH changes in the bitch in the follicular phase?

A

Mid/late anestrus:
Low LH levels and pulsatility
<1ng/ml

1 weeks before proestrus
Frequency increases to every 60-90m
Levels -3ng/ml

Proestrus
LH becomes lower and pulses less dectable

Late proestrus
LH peaks at 8-15ng/ml

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7
Q

How does FSH change in the bitch in the follicular phase?

A

Mid/late anestrus:
Levels are high and increase throughout anestrus

1 weeks before proestrus
Modest increase in FSH

Proestrus
FSH levels low

Late proestrus
Peak -1days after LH surger
Modest increase in mean level

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8
Q

How does oestradiol change in the bitch for the follicular phase?

A

Mid/late anestrus:
Remains low

1 weeks before proestrus
Low

Proestrus
Increases throughout from 10pg/ml => 120

Late proestrus
Peak levels are reaches 1 to 3 days before LH surge

Diestrus
Some secretion of oestrodiol

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9
Q

Describe changes in progesterone for the follicular phase…

A

Mid/late anestrus:
Low

1 weeks before proestrus
Low

Proestrus
Increases slowly

Late proestrus
2-4ng/ml at time of LH surger
4-10ng/ml at ovulation

Diestrus
Peak values of 15-19ng/ml

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10
Q

What are the events following the peak of oestradiol?

A

LH surger immediately after
Estrus behaviour
Both LH surge and behaviour said to initiated by decreased E;P ratiio
Ovulation 2d after LH surger

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11
Q

What unusual about ovulation in the bitch?

A

Oocytes that are ovulated are immature
i.e. not completed 1st meiotic division
Rising levels of P4 could be the signal for completeion of 1st meiotic division

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12
Q

How do progesterone levels change in the luteal phase in the bitch? How does this vary in pregnant and non-pregnant animals?

A

Progesterone increases and plateaus during diestrus and declines rapidly at luteolysis

This profile occurs in BOTH non-pregnant and pregnancy

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13
Q

What are the sources of progesterone during pregnancy in the bitch?

A

CL are the only source of progesterone during pregnanct

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14
Q

What hormones regulate progesterone secretion in the luteal phase (diestrus)?

A

LH
- GnRH agonist leads to luteolysis

Progesterone

  • regulates CLs ability to secrete progesterone
  • Inhibits luteal PGF2-alpha

PRL
- Regulates progesterone secretion from -day 25

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15
Q

Describe luteolysis in the dog…

A

Premature luteolysis = abortion
No known luteolysin in bitch
PGF receptor present and active throughout
PRL/LH receptirrs expressed throughout
In pregnant bitch, rapid pre-partum luteolysis due to foetoplacental PGF2-alpha release - essential for onset of parturition

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16
Q

How can luteolysis be induced in the bitch?

A 
PGF2-alpha at high doses
Progesterone receptor antagonist
GnRH antagonist
GnRH agonist (continously)
PRL lowering doses of dopamine agonist
17
Q

What does prolactin do in the bitch?

A

4X greater in pregnant animals
If block PRL release using dopamine agonists => functional demise of CL and abortion

Clinical signs of pseudopregnancy seem to be associated with an increase in PRL levels

18
Q

What are the clinical signs of pseudopregnancy?

A

Extensive mammary development
Lactation
Behavioural changes

19
Q

When are levels of relaxin raised?
What’s special about relaxin in the bitch/why is it useful?
What hormone does the increase in relaxin coincide with?

A 
Elevated -21-24d after LH surge
Non-detectable in non-pregnant animal
Sole source in the placenta
The ONLY specific pregnancy associated protein in the bitch - used for diagnosis 
Fall after parturition 
Increase coincides with rise in PRL
20
Q

How can oestrus be controlled in the bitch?

A

OVH
Progesterone
Testosterone

21
Q

What’s pseudopregnancy? What is it caused by and when is it seen?

A

Many non-pregnant animals exhibit signs from 45d after oestrus
Duration of luteal phase and progesterone concentration are normal
Associated with rise in plasma PRL

22
Q

What potentiates the development of pseudopregnancy? How can it be treated?

A

Any event leading to a fall in progesterone usually potentiates the development:
- OVH
- Lysis of CL
Treat with synthetic progestagens which suppresses PRL release

23
Q

Describe the characteristics of queen’s oestrus cycle. How is proestrus different to the bitch?

A

The queen is seasonally polyoestrus, induced ovulator, where oocytes are released only AFTER mating
There is NO prooestrus phase and oestral behaviour occurs with few changes of external genitalia

24
Q

What causes LH to rise in the queen? What happens after an infertile mating?

A

Copulation leads to rapid release of LH from the pituitary
Usually multiple copulations are required to produce sufficient LH to induce ovulation
Mating-induced luteal phase that is known as pseudopregnancy is the mating is infertile

25
Q

How do progesterone levels change in the queen?

A

Baseline until mating induced LH surge
Levels increase coincidentally with ovulation and peak after 30 days
In non-pregnant levels decrease
In pregnant levels maintained for further 25-28 days
Queens that have ovulated but no pregnant do not return to oestrus until after the levels of progesterone have fallen to baseline

26
Q

Describe changes in PRL in the queen…

A

Elevated for last 20days of prg and throughout lactation

No changes in levels of PRL during psuedopregancy

27
Q

Describe the interoestrous interval in the cat and how this can be changes with mating…

A

May be useful guide to whether ovulation or conception has failed to occur

Unmated queen, or mated queens that fail to ovulate have a interoestrus interval of 21 days

Mated queens that ovulate to fail to conceive have an interoestrus interval of approx 50days

Mated queens that become pregnant have a luteal phase of -65days

28
Q

What’s the non-pregnancy luteal phase in the queen called?

A

Pseudopregnancy

This could occur after mating or spontaneous ovulation

29
Q

How are signs of pseudopregnancy different in queens to bitches?

A

The clinical signs are an absence of oestrus. Unlike in the bitch, mammary development etc are NOT clinical signs

30
Q

How can oestrus be controlled in the cat?

A

OVH
hCG - induces ovulation and delays subsequent calling
Androgens - postpone calling if give -30d before anticipates oestrus
Progesterone - prevention - give as soon as signs of calling, suppress call and prevent conception

Reproduction (22 decks)

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