Hormonal Therapeutics

Question 1

two hormones released by the posterior pituitary are

Answer 1

oxytocin and antidiuretic hormone

Question 2

hormones can generally be classified as ____ or ____, based on where they bind

Answer 2

lipid-soluble (bind to targets inside cell) or water soluble (bind to cell surface targets)

Question 3

eicosanoids (prostaglandins and related compounds; they are involved in intracellular signalling) are produced from _______

Answer 3

arachidonic acid

Question 4

give 4 key points about hormones

Answer 4

synthesis depends on a variety of factors (age, repro status, sex, env factors); hormone secretion is not constant; signalling requires 3 key events; endocrine systems are controlled by feedback loops

Question 5

the estrus cycle is controlled by (A) secretion from the hypothalamus, which acts locally on the pituitary to stimulate (B) secretion. (B) causes follicular maturation; as follicles mature they secrete (C) which eventually causes a (D) spike, triggering ovulation. give A, B, C, D.

Answer 5

GnRH; FSH; estrogen; LH

Question 6

why bother synchronizing estrus in cattle? give at least 1 reason

Answer 6

estrus detection is hard; improves poor conception rates; synchronized carvings

Question 7

what are 4 reproductive therapeutics used to manipulate the estrous cycle

Answer 7

GnRH, PGF2 alpha, progesterone, estrogen

Question 8

PGF2 alpha promotes what and relaxes what?

Answer 8

promotes luteolysis and uterine contraction, relaxes cervix

Question 9

PGF2 alpha can cause what 2 bad things in humans?

Answer 9

bronchospasm or miscarriage… wear gloves

Question 10

what are 2 forms of hormonal therapeutic PGF2 alpha

Answer 10

dinoprost (naturally occurring prostaglandin, labelled for cattle, horses, swine) and cloprostenol (synthetic prostaglandin analogue, for cattle and swine).

Question 11

gonadorelin and perforelin are synthetic ____ agonists and cause a surge-like release of FSH and LH; used to treat cystic ovaries and estrous sync in cattle

Answer 11

GnRH

Question 12

_____ causes the behavioural effects of estrus and is not widely used in vet med due to human safety concerns

Answer 12

estrogen

Question 13

give 2 forms of estrogen. which is natural and which is synthetic

Answer 13

estradiol cypionate ECP is natural. diethylstilbestrol DES is synthetic.

Question 14

give at least 2 adverse effects of estrogen

Answer 14

uterine cancer, bone marrow suppression. also endometrial hyperplasia, SA lower seizure threshold, prolonged estrus, cyst development, cattle decreased lactation

Question 15

the most commonly used hormone in theriogenology is ____. in cattle a form of this called ______ is inserted in the vagina for 7 days to start anestrus cows cycling

Answer 15

progesterone; CIDR controlled internal drug release

Question 16

horses are _____ ______: anestrous in winter, cycling triggered by lengthening days in spring

Answer 16

seasonally polyestrous

Question 17

cows are _______ ______estrous

Answer 17

aseasonally polyestrous

Question 18

why induce ovulation in mares

Answer 18

have 21 day cycle, willingness to show estrus varies, and ovulated egg only viable for 12 hours

Question 19

what 2 hormonal therapeutics can induce ovulation in mares

Answer 19

hCG human chorionic gonadotropin and deslorelin (synthetic GnRH analogue, not licensed for vet use in Canada)

Question 20

what is estrous manipulation much less common in SA than LA

Answer 20

side effects and unreliable

Question 21

what to give to maintain equine pregnancy

Answer 21

progesterone. common in high risk mares

Question 22

why induce parturition in cattle

Answer 22

more postpartum time before next breeding; reduce calf size and dystocia; prevent excessive udder edema, take adv of forage available for lactation

Question 23

what 2 drugs can be used to induce parturition in cattle

Answer 23

GCs eg. dexamethasone (mimic fetal cortisol surge), prostaglandin (similar results), or both combined (faster results). they are mimicking fetal stress.

Question 24

why is induction of parturition in horses rarely done

Answer 24

variable gestation lengths, rarely necessary. when done though, we use oxytocin

Question 25

retained fetal membranes are common in cattle. what are a couple of options to treat?

Answer 25

systemic antibiotics if fever, PGF2alpha, collagenase (super expensive, used rarely), or do nothing

Question 26

are retained fetal membranes more of an emergency in horses or cows

Answer 26

horses

Question 27

what non steroidal estrogen is used in Canada as a cattle growth promoting

Answer 27

zeranol

Question 28

what are 3 reasons to use hormonal growth promoters in beef cattle

Answer 28

increased feed efficiency, economic benefit, and leaner meat

Question 29

describe thyroid hormone synthesis briefly

Answer 29

ingested iodine taken up by thyroid gland and secreted into colloid as iodide, iodide binds to thyroglobulin tyrosine and then thyroid peroxidase couples these residues to create T3 or T4; when thyroid stimulated to secrete TH (by TSH) the thyroglobulin is endocytose and T4/T3 are released into circulation

Question 30

which has more biological activity, T3 or T4

Answer 30

T3

Question 31

hypothyroidism should lead to _____ TSH due to negative feedback loops, while hyperthyroidism should lead to ____ TSH, but in cats TSH assay may not be reliable so TSH testing is recommended when diagnosing disease

Answer 31

high; low

Question 32

___thyroidism is one of the most common diseases of middle-aged to older cats; 98% of these cases are due to benign thyroid hyperplasia

Answer 32

hyperthyroidism

Question 33

what drug is used to treat hyperthyroidism in cats

Answer 33

methimazole. it reduced the amount of T4 and T3 secreted, but it doesn’t affect T3 and T4 already in tissues or circulation. it takes effect over several weeks

Question 34

this thyroid drug is usually given orally, bioavailability is variable, half life 2-10 hours, metabolized in liver, and is capable of crossing placenta. when used, total T4 and CBC should be monitored every 3 weeks for 3 months, then total T4 at 3-6 month intervals

Answer 34

methimazole (used for hyperthyroid cats)

Question 35

what 4 things is diagnosis of hypothyroidism in dogs based on

Answer 35

total T4, free T4, TSH, C/S. note considerable overlap between normal T4 values and hypothyroid range.

Question 36

this thyroid drug has a large first pass effect, absorbed best on empty stomach, large percentage excreted in bile, bioavailability varies based on formulation, dosing 1-2x daily, and requires monitoring 1-2 month after starting treatment total T4 at plea and then recheck 2-4 weeks after any dosage change

Answer 36

levothyroxine (used for hypothyroid dogs)

Question 37

what is used to treat hypothyroidism in dogs? Is it a form of T3 or T4?

Answer 37

levothyroxine. L-T4, a synthetic T4

Question 38

MOA of insulin

Answer 38

bind to insulin receptor tyrosine kinase to induce translocation of GLUT4 (transporter) to cell membrane, promoting glucose uptake by cells

Question 39

normally, insulin is secreted by pancreatic beta cells in response to ____ (increased or decreased?) blood glucose concentrations. insulin causes _____ of glucose by cells, _____ glucose production by liver, and _____ glycogen production by liver. all has the effect of lowering blood glucose.

Answer 39

increased, uptake, suppresses, promotes

Question 40

what is major adverse effect of insulin

Answer 40

hypoglycaemia if too much insulin or inadequate food intake. can be life-threatening

Question 41

cats usually have type ___ diabetes, while dogs sully have type _

Answer 41

cats type II (insulin resistance causing pancreatic beta cell failure); dogs type I (primary destruction of the beta cells, often immune mediated)