Hormones Flashcards
how do we use hormonal drug therapy?
replace a hormone deficiency
prevent or reduce the formation or effects of an overactive hormone
test for the presence of an endocrine disease
what does corticotropin-releasing hormone (CRH) stimulate?
synthesis and secretion of POMC and ACTH by pituitary corticotrophs
during a CRH (corticotropin releasing hormone) stimulation test, how does a primary adrenal insufficiency show up?
high basal plasma immunoreactive ACTH concentrations and show exaggerated responses to CRH
during a CRH (corticotropin releasing hormone) stimulation test, how does a secondary adrenal insufficiency show up?
undetectable basal plasma concentrations of ACTH that do not increase after CRH stimulation
what does ACTH stimulate?
secretion of glucocorticoids, mineralocorticoids, and adrenal androgens
why is an ACTH stimulation test performed?
to distinguish between adrenocortical hyperplasia and adrenocortical neoplasia in dogs, cats, and horses
what is trilostane?
a steroidogenesis inhibitor (3beta-hydroxysteroid dehydrogenase)
what is mitotane?
chlorinated hydrocarbon (derivative of DDT)
what is mitotane specific for?
adrenal glands, particularly hyperplasia gland
why is a TRH test performed?
to diagnose pituitary and thyroid disease
why is a TSH test performed?
thyroid disease
hypothyroidism
what does a TRH test evaluate?
pituitary’s responsiveness to TRH as manifested by the change in serum TSH
what is the most common endocrine disease in dogs?
hypothyroidism
what does a TSH test evaluate?
thyroid responsiveness to TSH by change in serum T4
what is the most common endocrine disease in cats?
hyperthyroidism
what are the signs of hyperthyroidism?
weight loss, increased appetite, increased thirst and urination
+/- vomiting, diarrhea, hyperactivity
coat may appear unkempt, matted or greasy
what is hypothyroidism treated with?
thyroid hormone replacement
what is the first choice for treating hypothyroidism?
Levothyroxine (L-T4)
how is hyperthyroidism treated?
antithyroid drugs
what do goitrogens do?
inhibit thyroid peroxidase (TPO)- catalyzed iodination
what do thioureylenes or thionamides do?
directly inhibit TPO
what are the primary adverse effects of the treatment for hyperthyroidism?
anorexia
vomiting
lethargy
what are the treatment options for hyperthyroidism?
goitrogens
thioureylenes or thionamides
radioactive iodine therapy
surgery
which neurons secrete growth hormone releasing hormone (GHRH)?
neurons in arcuate nucleus
what synthesizes and secretes growth hormone?
somatotrophs
what stimulates growth hormone releasing hormone?
ghrelin
what are the therapeutic uses of somatotropin (growth hormone)?
pituitary dwarfism
more uses in large animals
what are some therapeutic uses of somatotropin (growth hormone) in large animals?
cattle, lamb, and pig to improve growth rates and protein/fat ratio
improve fertilization rate, accelerate embryo development and improve embryo survival
increase milk production in the cow
what are the posterior pituitary hormons?
vasopressin (antidiuretic hormone)
oxytocin
where is antidiuretic hormone synthesized?
hypothalamus
what are the adverse effects in dogs of somatotropin (growth hormone)?
diabetes mellitus
what does antidiuretic hormone regulate?
water permeability of the distal tubules and collecting duct of the nephron
what is diabetes insipidus (DI) caused by?
deficiency of antidiuretic hormone (central DI) or absence of renal response to ADH (nephrogenic DI)
what is the therapeutic use of antidiuretic hormone?
central diabetes insipidus
how is oxytocin used?
induce milk letdown and uterine contraction
induction of parturition and treatment of pyometra
what are the two primary hypothalamic hormones for reproduction?
gonadotropin releasing hormone (GnRH)
prolactin-inhibitory hormone, dopamine
what does gonadotropin releasing hormone (GnRH) stimulate?
release of follicle stimulating hormone and luteinizing hormone
what is gonadotropin releasing hormone (GnRH) used for?
induce ovulation or follicular luteinization
suppress gonadotropin secretion (medical castration)
what is gonadorelin?
synthetic GnRH
what is the action of gonadorelin?
stimulate synthesis and secretion of FSH and LH by interaction with the GnRH receptors in the pituitary
what does LH do to testicular leydig cells?
stimulates them to synthesize androgens (testosterone)
what does FSH do in males?
acts on sertoli cells to stimulate production of proteins and nutrients required for regulation of sperm production and maturation
are there primary therapeutic uses for prolactin?
no
how is hCG used?
infertility therapy in horses
cystic ovaries in cows
follicle development in pigs
male infertility due to impotence in stallion
induction of pseudopregnancy in cats and fertile estrus in dogs (hCG then eCG)
what does oxytocin do?
stimulates frequency and force of uterine contraction
plays a role in milk ejection
what are the clinical uses of oxytocin?
induce labor
milk letdown
persistent postmating endometritis (mare)
inhibition of cyclicity (mare)
what does removal of progestin do?
initiates a new estrous cycle and ovulation
what is the primary circulating androgen in males?
testosterone
what is finasteride?
irreversible 5alpha-reductase inhibitor
what is regular insulin used to treat?
primarily ketoacidosis
what hormones are produced by the pars distalis?
growth hormone
luteinizing hormone
follicle stimulating hormone
ACTH
prolactin
thyrotropin stimulating hormone
what does the posterior/rostral lobe of the pituitary gland do?
stores and releases oxytocin and antidiuretic hormone produced in the hypothalamus
why is trilostane used in cushings?
inhibits production of corticosteroids such as cortisol and aldosterone
what does mitotane do?
adrenocorticolytic: progressive necrosis of the zona fasciculata, zona reticularis, and zona glomerulosa
what does thyrotropin releasing hormone lead to?
thyrotropin stimulating hormone, which stimulates the thyroid to release T4
what does the TRH and TSH stimulation test evaluate?
thyroid responsiveness to TSH by change in serum T4
what is a TSH stimulation test used to confirm?
hypothyroidism
what are the clinical signs of hypothyroidism?
loss or thinning of fur
dull hair coat
excess shedding or scaling
weight gain
reduced activity
reduced ability to tolerate cold
what are the clinical signs of hyperthyroidism?
weight loss
increased appetite
pu/pd
+/- vomiting, diarrhea, hyperactivity
coat may appear unkempt, matted, or greasy
how frequent is toxicity from levothyroxine (L-T4)?
rare: efficiently cleared by biliary and fecal excretion
what are the most commonly used antithyroid drugs?
thionamides (methimazole and carbimazole)
what is growth hormone releasing hormone stimulated by?
ghrelin
what does growth hormone releasing hormone stimulate?
synthesis and secretion of growth hormone by somatotrophs
what inhibits growth hormone releasing hormone?
somatostatin
what are somatostatin analogues used for?
manage pituitary disorders: acromegaly, gastrinoma, pancreatic beta cell tumors, glucagonoma
what is used to treat acromegaly specifically?
pegvisomant: growth hormone receptor antagonist
how does antidiuretic hormone influence cardiovascular function?
vasoconstrictor
antidiuretic hormone is synthesized by the _________________ and secreted via the __________________________
hypothalamus
neurohypophyseal system
what are the uses of gonadorelin?
ovulation induction
cystic ovaries
estrus synchronization
timed embryo transfer protocol
terminate estrus in induced ovulators and ferrets
long-acting GnRH agonists inhibit cyclicity in domestic dogs and cats
what do FSH and LH do in females?
stimulate the growth and development of ovarian follicles
LH induces ovulation and stimulates the developing corpus luteum to secrete progesterone
what is human chorionic gonadotropin used for?
infertility therapy in horses
cystic ovaries in cows
follicle development in pigs
male infertility due to impotence in stallion
induction of pseudopregnancy in cats and fertile estrus in dogs
what is equine chorionic gonadotropin used for?
stimulate ovarian follicular growth in anestrous sheep or goat
induction of ovulation and formation of corpus luteum
follicle development in pigs
induction of pseudopregnancy in cats and fertile estrus in dogs
what are drugs that inhibit prolactin used for?
termination of pregnancy
treatment of pseudopregancy
pyometra
estrus induction in dogs and cats
why are estrogens not used in food animals?
concerns over food residues in meat
where does progesterone act?
progesterone receptors in hypothalamus and pituitary: increase negative feedback and decrease FSH and LH output
who is long-acting insulin used in?
dogs and cats
who is intermediate-acting insulin used in?
dogs