Non-Surgical Control

Question 1

Where is GnRH secreted from?

Answer 1

The hypothalamus

Question 2

GnRH has a direct effect on secretion of what hormone(s)?

Answer 2

FSH & LH

Question 3

Estradiol creates negative feedback on what hormone(s)?

Answer 3

GnRH & FSH

Question 4

What is/are the function(s) of Prolactin?

Answer 4

1. Luteotrophic (helps to maintain CL during diestrus)
2. Primes body for lactation

Question 5

How long is the interestrus interval in a dog?

Answer 5

4-12 months

Question 6

How long (on average) is proestrus in the dog? What about estrus?

Answer 6

9 days on average for both

Question 7

Diestrus/anestrus (choose one) is the time for uterine involution & remodeling (i.e. desquamation of endometrium).

Answer 7

Anestrus

Question 8

Who are candidates for estrus control?

Answer 8

1. Working dogs
2. Dogs w/ congenital abnormalities or high risk surgical candidates

Question 9

What drug class are Megestrol acetate (MGA) & Medroxyprogesterone acetate (MPA)?

Answer 9

Synthetic progestins

Question 10

What is the mechanism of action of synthetic progestins?

Answer 10

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

Question 11

Why are synthetic progestins preferred over other progestins?

Answer 11

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

Question 12

When should you give progestins?

Answer 12

1. When bitch is in anestrus (give once daily for 7 days)
2. When in early proestrus (dog would have started bleeding & have swelling of vulva but needs to stop the estrous cycle due to her job)

Question 13

T/F: It is okay to give progestins in late proestrus or estrus.

Answer 13

F, it is too late at this point to stop follicular development to prevent ovulation

Question 14

Which dogs should you NOT use progestins?

Answer 14

1. Prior to pubertal heat
2. Don’t use for 2 consecutive cycles (increases risk for developing CEH & pyometra)
3. Concurrent comorbidities (reproductive tissue disease, liver disease, pregnant, or older bitches)

Question 15

What risks do Progestins pose?

Answer 15

1. Could lead to pyometra (closes the cervix, quiescence of uterus, endometrium proliferation, etc.)
2. Metabolic issues (if high affinity for glucocorticoid receptors -> diabetes, acromegaly)
3. Increased appetite & aggressive behavior

Question 16

What drug class is Mibolerone?

Answer 16

Synthetic weak androgen

Question 17

What is the mechanism of action of Mibolerone?

Answer 17

Suppression of HPO axis due to negative feedback on hypothalamus (prevents GnRH & LH secretions)

• Has direct effect on estrogen receptors due to sensitivity

Question 18

What is the protocol of using Mibolerone?

Answer 18

• Start in first half of anestrus & give orally daily

Question 19

You should not use what type of estrus control medication in Bedlington terriers due to copper storage disease for liver?

Answer 19

Mibolerone (synthetic weak androgen)

Question 20

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.

Answer 20

T

Question 21

Name some side effects of Mibolerone

Answer 21

• Galactorrhea, false pregnancy, aggression
• Increases testosterone, so may see masculinization of dog, clitoral hypertrophy, vulvar discharge, etc.

Question 22

When should Mibolerone not be used?

Answer 22

• Prior to pubertal heat
• Repro pathology present
• Liver or renal disease
• Bedlington terriers

Question 23

What drug class is Deslorelin?

Answer 23

GnRH super agonist (aka synthetic GnRH analog)

This will bind to GnRH receptors better than natural GnRH

Question 24

What is the mechanism of action of Deslorelin?

Answer 24

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

Question 25

Can you reverse the suppression of fertility created by Deslorelin?

Answer 25

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.

Question 26

Where should Deslorelin be implanted in the bitch?

Answer 26

Near the umbilical area; mark where you put it in the record so that you can remove it later

Question 27

For long-term estrus prevention, how often should you re-implant Deslorelin?

Answer 27

Every 4-4.5 months in dogs

Question 28

Why might you induce estrus in the bitch?

Answer 28

1. Concerned for secondary anestrus (i.e. > 12 month interestrus interval)
2. Young breeding bitches, normal repro tract, & no obvious pathology

Question 29

Is it practical to use gonadotrophins in dogs to induce estrus?

Answer 29

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

Question 30

What medication used for estrus suppression can also be used to induce estrus in the bitch?

Answer 30

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!