Hormonal Therapeutics Flashcards
two hormones released by the posterior pituitary are
oxytocin and antidiuretic hormone
hormones can generally be classified as ____ or ____, based on where they bind
lipid-soluble (bind to targets inside cell) or water soluble (bind to cell surface targets)
eicosanoids (prostaglandins and related compounds; they are involved in intracellular signalling) are produced from _______
arachidonic acid
give 4 key points about hormones
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
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.
GnRH; FSH; estrogen; LH
why bother synchronizing estrus in cattle? give at least 1 reason
estrus detection is hard; improves poor conception rates; synchronized carvings
what are 4 reproductive therapeutics used to manipulate the estrous cycle
GnRH, PGF2 alpha, progesterone, estrogen
PGF2 alpha promotes what and relaxes what?
promotes luteolysis and uterine contraction, relaxes cervix
PGF2 alpha can cause what 2 bad things in humans?
bronchospasm or miscarriage… wear gloves
what are 2 forms of hormonal therapeutic PGF2 alpha
dinoprost (naturally occurring prostaglandin, labelled for cattle, horses, swine) and cloprostenol (synthetic prostaglandin analogue, for cattle and swine).
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
GnRH
_____ causes the behavioural effects of estrus and is not widely used in vet med due to human safety concerns
estrogen
give 2 forms of estrogen. which is natural and which is synthetic
estradiol cypionate ECP is natural. diethylstilbestrol DES is synthetic.
give at least 2 adverse effects of estrogen
uterine cancer, bone marrow suppression. also endometrial hyperplasia, SA lower seizure threshold, prolonged estrus, cyst development, cattle decreased lactation
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
progesterone; CIDR controlled internal drug release
horses are _____ ______: anestrous in winter, cycling triggered by lengthening days in spring
seasonally polyestrous
cows are _______ ______estrous
aseasonally polyestrous
why induce ovulation in mares
have 21 day cycle, willingness to show estrus varies, and ovulated egg only viable for 12 hours
what 2 hormonal therapeutics can induce ovulation in mares
hCG human chorionic gonadotropin and deslorelin (synthetic GnRH analogue, not licensed for vet use in Canada)
what is estrous manipulation much less common in SA than LA
side effects and unreliable
what to give to maintain equine pregnancy
progesterone. common in high risk mares
why induce parturition in cattle
more postpartum time before next breeding; reduce calf size and dystocia; prevent excessive udder edema, take adv of forage available for lactation
what 2 drugs can be used to induce parturition in cattle
GCs eg. dexamethasone (mimic fetal cortisol surge), prostaglandin (similar results), or both combined (faster results). they are mimicking fetal stress.
why is induction of parturition in horses rarely done
variable gestation lengths, rarely necessary. when done though, we use oxytocin
retained fetal membranes are common in cattle. what are a couple of options to treat?
systemic antibiotics if fever, PGF2alpha, collagenase (super expensive, used rarely), or do nothing
are retained fetal membranes more of an emergency in horses or cows
horses
what non steroidal estrogen is used in Canada as a cattle growth promoting
zeranol
what are 3 reasons to use hormonal growth promoters in beef cattle
increased feed efficiency, economic benefit, and leaner meat
describe thyroid hormone synthesis briefly
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
which has more biological activity, T3 or T4
T3
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
high; low
___thyroidism is one of the most common diseases of middle-aged to older cats; 98% of these cases are due to benign thyroid hyperplasia
hyperthyroidism
what drug is used to treat hyperthyroidism in cats
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
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
methimazole (used for hyperthyroid cats)
what 4 things is diagnosis of hypothyroidism in dogs based on
total T4, free T4, TSH, C/S. note considerable overlap between normal T4 values and hypothyroid range.
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
levothyroxine (used for hypothyroid dogs)
what is used to treat hypothyroidism in dogs? Is it a form of T3 or T4?
levothyroxine. L-T4, a synthetic T4
MOA of insulin
bind to insulin receptor tyrosine kinase to induce translocation of GLUT4 (transporter) to cell membrane, promoting glucose uptake by cells
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.
increased, uptake, suppresses, promotes
what is major adverse effect of insulin
hypoglycaemia if too much insulin or inadequate food intake. can be life-threatening
cats usually have type ___ diabetes, while dogs sully have type _
cats type II (insulin resistance causing pancreatic beta cell failure); dogs type I (primary destruction of the beta cells, often immune mediated)
