Non-Surgical Control Flashcards
Where is GnRH secreted from?
The hypothalamus
GnRH has a direct effect on secretion of what hormone(s)?
FSH & LH
Estradiol creates negative feedback on what hormone(s)?
GnRH & FSH
What is/are the function(s) of Prolactin?
- Luteotrophic (helps to maintain CL during diestrus)
- Primes body for lactation
How long is the interestrus interval in a dog?
4-12 months
How long (on average) is proestrus in the dog? What about estrus?
9 days on average for both
Diestrus/anestrus (choose one) is the time for uterine involution & remodeling (i.e. desquamation of endometrium).
Anestrus
Who are candidates for estrus control?
- Working dogs
- Dogs w/ congenital abnormalities or high risk surgical candidates
What drug class are Megestrol acetate (MGA) & Medroxyprogesterone acetate (MPA)?
Synthetic progestins
What is the mechanism of action of synthetic progestins?
Has direct effect on ovary to bind & cause negative feedback on the HPO axis, thus reducing GnRH production/secretion, which will ultimately decrease production/secretion of FSH & LH. Thus, it is stopping follicular development.
It will also reduce prolactin production due to stopping the negative effect on the pituitary
Why are synthetic progestins preferred over other progestins?
Progesterone is also made at the adrenal glands, so certain progestins may have an effect on anabolic steroids & metabolism -> can lead to diabetic issues (insulin resistance) or poor glucose metabolism & acromegaly
Synthetic progestins are more targeted to the reproductive tract for function & effect
When should you give progestins?
- When bitch is in anestrus (give once daily for 7 days)
- When in early proestrus (dog would have started bleeding & have swelling of vulva but needs to stop the estrous cycle due to her job)
T/F: It is okay to give progestins in late proestrus or estrus.
F, it is too late at this point to stop follicular development to prevent ovulation
Which dogs should you NOT use progestins?
- Prior to pubertal heat
- Don’t use for 2 consecutive cycles (increases risk for developing CEH & pyometra)
- Concurrent comorbidities (reproductive tissue disease, liver disease, pregnant, or older bitches)
What risks do Progestins pose?
- Could lead to pyometra (closes the cervix, quiescence of uterus, endometrium proliferation, etc.)
- Metabolic issues (if high affinity for glucocorticoid receptors -> diabetes, acromegaly)
- Increased appetite & aggressive behavior
What drug class is Mibolerone?
Synthetic weak androgen
What is the mechanism of action of Mibolerone?
Suppression of HPO axis due to negative feedback on hypothalamus (prevents GnRH & LH secretions)
- Has direct effect on estrogen receptors due to sensitivity
What is the protocol of using Mibolerone?
- Start in first half of anestrus & give orally daily
You should not use what type of estrus control medication in Bedlington terriers due to copper storage disease for liver?
Mibolerone (synthetic weak androgen)
T/F: Mibolerone causes temporary suppression/prevention of estrous cycling & should not be used for longer than 2 years due to the side effects & risk factors.
T
Name some side effects of Mibolerone
- Galactorrhea, false pregnancy, aggression
- Increases testosterone, so may see masculinization of dog, clitoral hypertrophy, vulvar discharge, etc.
When should Mibolerone not be used?
- Prior to pubertal heat
- Repro pathology present
- Liver or renal disease
- Bedlington terriers
What drug class is Deslorelin?
GnRH super agonist (aka synthetic GnRH analog)
This will bind to GnRH receptors better than natural GnRH
What is the mechanism of action of Deslorelin?
Implant, so there will be a continuous release of GnRH -> body becomes desensitized to it -> pituitary stops responding to GnRH & removes the receptors from its surface -> stops FSH & LH secretion -> no estrous cycle
Can you reverse the suppression of fertility created by Deslorelin?
Yes, but it is variable for each dog. The body needs time to turn natural GnRH pulse release back on.
There are subcutaneous implants available (Superlorin F (off-label use in dogs)) but there are a lot of FDA restrictions. You need a very valid reason to need this drug.
Where should Deslorelin be implanted in the bitch?
Near the umbilical area; mark where you put it in the record so that you can remove it later
For long-term estrus prevention, how often should you re-implant Deslorelin?
Every 4-4.5 months in dogs
Why might you induce estrus in the bitch?
- Concerned for secondary anestrus (i.e. > 12 month interestrus interval)
- Young breeding bitches, normal repro tract, & no obvious pathology
Is it practical to use gonadotrophins in dogs to induce estrus?
No, need very frequent administration of drugs & creates risk for anovulatory cycle or luteal failure
Can also cause split heat if not appropriately dosing or pulse frequency
What medication used for estrus suppression can also be used to induce estrus in the bitch?
Deslorelin implant; this time, we are only using it for the flare up effect (body thinks there is an increase in GnRH to stimulate follicular development)
Implanted during anestrus & removed prior to ovulation!
