Endocrine (repro/thyroid) Flashcards
Why might we need to manipulate the estrous cycle in cattle?
- It is difficult to tell when a cow is in estrus.
- To improve conception rates.
- To synchronize calving.
What are the four hormones used to manipulate the estrous cycle?
- Prostaglandin
- GnRH
- Progesterone
- Estrogen
What is the function of GnRH? Where is it released from?
GnRH is released from the hypothalamus and tells the anterior pituitary to release a surge of FSH and LH. It triggers the LH spike that induces ovulation.
What is the function of prostaglandin? Where is it released from?
Prostaglandin (PGF2α) is secreted by the endometrium and promotes luteolysis and uterine contraction, and relaxes the cervix.
True or False: All prostaglandins may cause adverse effects in mares.
True
True or False: Small animals are more sensitive to the effects of prostaglandin.
True
What are two differences between Dinoprost and Cloprostenol? (Both are PGF-2a)
- Dinoprost is labelled for cattle, horses, and swine, but Cloprostenol is labelled for cattle and swine only. However, Cloprostenol is still used for horses due to fewer side effects.
- Dinoprost has a shorter half-life.
What is the function of progesterone? Where is it released from?
Progesterone is secreted by the corpus luteum and sends negative feedback to the anterior pituitary to stop FSH and LH production. It prevents ovulation and maintains pregnancy.
What is the function of estrogen? Where is it released from?
Estrogen is secreted by the granulosa cells in the follicle and causes estrus behavior. It also induces the LH spike and stimulates mammary development.
True or False: Estrogen is commonly used in veterinary medicine.
False. It is not widely used in vet med, especially not in food animals because of human health/food safety concerns.
True or False: Manipulating the estrous cycle is the same protocol in beef as it is in dairy cattle.
True
What is a CIDR (controlled internal drug release) device?
An intravaginal progesterone insert used in conjunction with hormones to synchronize estrus in dairy cows.
Which hormone is the active ingredient in a CIDR?
Progesterone
What is Melengestrol acetate (MGA)?
An oral form of progesterone that suppresses estrus in feedlot heifers.
Why might we need to manipulate the estrous cycle in horses?
- To move the cycling season earlier.
- To shorten the transition between non-cycling and cycling.
- To induce ovulation.
- To suppress ovulation.
Which two drugs are used for inducing ovulation in mares?
- Human chorionic gonadotropin (hCG)
- Deslorelin (a synthetic GnRH analogue)
What is the most common drug used in theriogenology?
Progesterone
What is progesterone mainly used for in horses?
To maintain pregnancy in high-risk mares.
Why is estrous cycle manipulation much less common in small animals than large animals?
It is very unreliable and small animals are a lot more sensitive to the side effects.
Why might we want to induce parturition in cows?
- To allow more postpartum time before next breeding.
- To attempt to reduce calf size/dystocia.
- To prevent excessive udder edema in dairy cattle.
- To take advantage of available forage for lactation.
What are two classes of drugs commonly used to induce parturition in cows?
- Glucocorticoids
- Prostaglandins
How do glucocorticoids and prostaglandins induce parturition in cows?
These drugs mimic fetal cortisol surges.
True or False: The combined use of glucocorticoids and prostaglandin will lead to faster induction of parturition in cattle.
True
True or False: Induction of parturition in mares is common.
False. This is not commonly done unless the mare is experiencing a life-threatening complication of pregnancy.
What is the one class of drug used to induce parturition in mares?
Oxytocin
Name six ways we can treat retained fetal membranes in cows.
- Do nothing.
- Systemic antibiotics if symptoms are shown.
- Use prostaglandin.
- Oxytocin.
- Collagenase.
- Calcium.
True or False: We treat retained fetal membranes the same way, whether it’s in cows or mares.
False!
Name five drugs we can use to treat retained fetal membranes in mares.
- Oxytocin
- Calcium
- NSAIDs
- Systemic antibiotics
- Prostaglandin
What is the one class of drug used to promote milk let-down in cows?
Oxytocin
Which drug(s) would be the best choice for induction of parturition in a cow?
A combination of glucocorticoids (dexamethasone) and prostaglandin.
Which drug(s) would be the best choice for induction of luteolysis in a cow?
Dinoprost or Cloprostenol.
Which drug(s) would be the best choice for induction of abortion in a cow (between days 30-110)?
Dinoprost or Cloprostenol.
Which drug(s) would be the best choice for induction of parturition in a mare?
Oxytocin.
Which drug(s) would be the best choice for maintaining a high-risk equine pregnancy?
Altrenogest (progesterone).
Which drug(s) would be the best choice for the treatment of retained fetal membranes in a mare?
Oxytocin.
What are the six functions of thyroid hormones?
- Increase metabolic rate.
- Increase sensitivity to catecholamines.
- Increase protein synthesis, glycogenolysis, and glycolysis.
- Positive inotrope.
- Stimulates immunity.
- Essential for growth and development.
Hypothyroidism should lead to _____ TSH because of lack of ______ feedback.
High, negative.
Hyperthyroidism should lead to _____ TSH because of lack of ______ feedback.
Low, negative.
How should you be monitoring levels of methimazole in cats diagnosed with hyperthyroidism?
A T4 and CBC is recommended every 2-3 weeks for the first 3 months, then T4 at 3-6 month intervals.
What does it take several weeks to see the full effects of methimazole?
Since methimazole only reduces production of T3 and T4 by the thyroid gland, it does not affect T3 and T4 that are already in tissues or circulation.
How should you be monitoring dogs after starting levothyroxine?
Monitor levels 1 - 2 months after starting treatment.
How should you be monitoring dogs on levothyroxine after a dose change?
Recheck 2 - 4 weeks after any dosage change.
What is the main goal in treatment using insulin?
To maintain blood glucose in a mildly hyperglycemic state (and AVOID hypoglycemia).
True or False: Hypoglycemia is more acutely dangerous than hyperglycemia.
True!
Describe insulin’s mechanism of action.
- Insulin binds to its receptor.
- Induces translocation of GLUT4 to the cell membrane.
- Promotes uptake of glucose in insulin-sensitive tissues and suppresses gluconeogenesis in the liver.
What does insulin do to potassium and magnesium levels?
Insulin causes potassium and magnesium to shift intracellularly.
Why are cats with urethral obstructions sometimes treated with insulin?
Because insulin causes magnesium and potassium to shift intracellularly.
What is a major adverse effect of insulin?
Hypoglycemia.
Cats usually develop which type of diabetes?
Type 2.
Dogs usually develop which type of diabetes?
Type 1.
