Reproductive Endocrinology in Small Animals Flashcards
What are the secretory products of the:
- Follicular phase
- Luteal phase
- Oestrogen dominant (E2)
2. Progesterone dominant
How is the oestrus cycle classified in terms of vaginal cytology?
Pro-oestrus: rise in oestrodiol
Oestrus: maximum oestrodiol
Metoestrus: transitional
Dioestrus: progesterone dominant
How can the reproductive physiology of the bitch and queen be described?
Bitch: Mono-oestrus Non-seasonal Polytocous Spontaneous ovulation
Queen:
Seasonally polyoestrus
Polytocous
Induced ovulator
- When does the bitch ovulate?
- What is follicular development regulated by?
- What is LH and FSH secretion regulated by?
- Ovulates spontaneously at end of variable follicular phase (4-28d)
- FSH and LH, which acts to synthesis oestradiol
- GnRH from the hypothalamus and steroids from the ovaries
What are the stages of the canine oestrus cycle?
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)
Describe how LH changes in the bitch in the follicular phase?
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
How does FSH change in the bitch in the follicular phase?
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
How does oestradiol change in the bitch for the follicular phase?
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
Describe changes in progesterone for the follicular phase…
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
What are the events following the peak of oestradiol?
LH surger immediately after
Estrus behaviour
Both LH surge and behaviour said to initiated by decreased E;P ratiio
Ovulation 2d after LH surger
What unusual about ovulation in the bitch?
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
How do progesterone levels change in the luteal phase in the bitch? How does this vary in pregnant and non-pregnant animals?
Progesterone increases and plateaus during diestrus and declines rapidly at luteolysis
This profile occurs in BOTH non-pregnant and pregnancy
What are the sources of progesterone during pregnancy in the bitch?
CL are the only source of progesterone during pregnanct
What hormones regulate progesterone secretion in the luteal phase (diestrus)?
LH
- GnRH agonist leads to luteolysis
Progesterone
- regulates CLs ability to secrete progesterone
- Inhibits luteal PGF2-alpha
PRL
- Regulates progesterone secretion from -day 25
Describe luteolysis in the dog…
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
How can luteolysis be induced in the bitch?
PGF2-alpha at high doses Progesterone receptor antagonist GnRH antagonist GnRH agonist (continously) PRL lowering doses of dopamine agonist
What does prolactin do in the bitch?
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
What are the clinical signs of pseudopregnancy?
Extensive mammary development
Lactation
Behavioural changes
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?
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
How can oestrus be controlled in the bitch?
OVH
Progesterone
Testosterone
What’s pseudopregnancy? What is it caused by and when is it seen?
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
What potentiates the development of pseudopregnancy? How can it be treated?
Any event leading to a fall in progesterone usually potentiates the development:
- OVH
- Lysis of CL
Treat with synthetic progestagens which suppresses PRL release
Describe the characteristics of queen’s oestrus cycle. How is proestrus different to the bitch?
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
What causes LH to rise in the queen? What happens after an infertile mating?
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
How do progesterone levels change in the queen?
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
Describe changes in PRL in the queen…
Elevated for last 20days of prg and throughout lactation
No changes in levels of PRL during psuedopregancy
Describe the interoestrous interval in the cat and how this can be changes with mating…
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
What’s the non-pregnancy luteal phase in the queen called?
Pseudopregnancy
This could occur after mating or spontaneous ovulation
How are signs of pseudopregnancy different in queens to bitches?
The clinical signs are an absence of oestrus. Unlike in the bitch, mammary development etc are NOT clinical signs
How can oestrus be controlled in the cat?
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
