4 Growth Hormone Disorders: Acromegaly - END EXAM 1 CONTENT

T/F Dr. Leisewitz is from France

False; he is from South Africa

what hormone from the hypothalamus inhibits GH secretion?

Somatostatin

what are the major adenohypophysis hormones of the pituitary gland? (6)

GH

TSH

ACTH

FSH

LH

PL

what are the major neurohypophysis hormones of the pituitary gland? (2)

oxytocin

ADH

describe the pathway and structures involved in the release of insulin-like growth factor (IGF-1) from the liver starting with the hypothalamus

hypothalamus releases GHRH -> stimulates the pituitary gland which releases GH -> stimulates the liver which releases IGF-1

What provides negative feedback to stop the release of GHRH from the hypothalamus?

GH

What provides negative feedback to stop the release of GH from the pituitary gland? (3)

Somatostatin (SS) from the hypothalamus

GH from the pituitary

IGF-1 from the liver

T/F IGF-1 can directly provide negative feedback to inhibit the release of GH from the pituitary gland but it can also indirectly inhibit the release of GH by stimulating the hypothalamus to release SS

True

What is another term for acromegaly?

hypersomatotropism

what are two possible pathophysiologies behind acromegaly in cats?

GH-secreting tumor (90% macroadenoma)

Hyperplasia?

what is the typical signalment for acromegaly in cats? (Age, gender, breed)

older (mean 10 years)

neutered males (88%)

no breed predisposition

What do cats with acromegaly commonly present with? (4)

insulin-resistant diabetes

stridor

heart failure (HCM)

neurological

why do cats with acromegaly develop stridor?

GH encourages growth of soft tissues (this is why organs may be enlarged as well)

what are the COMMON history and clinical signs of cats with acromegaly? (5)

pu/pd (87%- many acromegaly cats are diabetic)

polyphagia (75%)

Weight loss

weight gain

stridor

what are the LESS COMMON history and clinical signs of cats with acromegaly? (3)

stiffness (early onset OA)

lameness

CHF

why might cats with acromegaly develop CHF?

excess GH can lead to myocardial hypertrophy -> HCM (low output CHF)

what are common physical exam findings in acromegaly cats? (9)

stridor (50%)

lameness/stiffness (40%)

abdominal organomegaly (40%)

clubbed paws (13%)

prognathia inferior (18%)

widening interdental spaces

broad facial features (40%)

enlarged tongue

murmur

T/F neurological signs due to acromegaly are common and result from the enlarged pituitary putting pressure on the optic chiasm that rests right above it. Vision problems are often some of the first neuro signs observed followed by other neuro signs as the tumor grows

False; neurological signs are UNCOMMON the rest of it is true

T/F owners may not appreciate changes like broadening of their cats facial features because the changes are so gradual

true

What would you expect to find on clinical pathology data in cats with acromegaly?

nothing specific

findings typical of diabetes

how can acromegaly be diagnosed in cats? (2)

IGF-1 levels (after 6-8 weeks of insulin)

CT/MRI

what is the definitive test for acromegaly in cats?

What important considerations do you need to have for this test?

IGF-1

patient needs to be on insulin for 6-8 weeks prior to testing

What are treatment options for cats with acromegaly? (3)

which does auburn prefer?

hypophysectomy

radiation therapy

medical therapy

radiation therapy

T/F with hypophysectomy and radiation therapy treatments of acromegaly, hormone supplementation will be needed because you aren't just losing the cells that secrete GH in the process, you are also losing cells that secrete other important hormones

true

with which acromegaly treatment is diabetes the most likely to resolve in cats?

hypophysectomy

T/F the median survival of cats with acromegaly that undergo radiation therapy treatment is 1072 days

true

T/F radiation therapy may be needed for neuro signs caused by acromegaly when surgery isn't possible

true

insulin dose is often reduced by __% with radiation therapy of acromegaly with ___ of cats undergoing remission (which may be transient)

95

1/3

why is it important to be careful about monitoring cats diabetes after radiation therapy for acromegaly?

cats are often on super high insulin doses. Blood glucose levels should be monitored very carefully after radiation therapy so that insulin doses can be quickly adjusted in response to glucose changes

what is the medical treatment of choice for acromegaly in cats?

SGLT2i + insulin

T/F SGLT2i + insulin are usually given to cats with acromegaly until radiation can be done - but its possibly helpful lifelong

true

what are two other medical therapies available for acromegaly?

what are their MOAs?

pasireotide- somatostatin analog

cabergoline - dopamine receptor agonist

without treatment, acromegaly in cats is life limiting due to effects of hypersomatotropism. What are some of these effects?

arthritis

stridor

heart failure

diabetes (hard to control, need high doses of insulin, sudden hypoglycemia possible)

what is the short-term and long-term prognosis for cats with acromegaly?

what is the typical length of survival for these patients?

short-term: guarded to good

long-term: poor

survival: 4-60 months

What are potential mechanisms of acromegaly in dogs? (3)

pituitary tumor (2 cases)

mammary tumors (rare)

progestin exposure

What is the main mechanism of acromegaly in dogs?

Progestin exposure

T/F progestin can help keep estrus from happening in dogs but it can lead to issues like pyometra and mammary gland tumors

true

Where is GH released from in dogs?

mammary glands

how might dogs be exposed to progestin? (2)

natural

iatrogenic

How does progestin affect GH production in dogs?

causes mammary production of GH

spontaneous acromegaly in dogs is (choose one: proestrus/estrus/diestrus/anestrus) related

diestrus (progesterone phase)

what is the typical signalment for spontaneous acromegaly in dogs? (think age, gender, and breed predispositions)

older

intact females

german shepherds

what is the typical signalment for iatrogenic acromegaly in dogs?

any dog

is acromegaly more common in dogs or cats?

cats

what is evidence on physical exam of excess growth hormone in dogs? (3)

stridor

lameness/stiffness

acromegaly

what are classic signs of acromegaly in dogs? (5)

enlarged tongue

excess skin folds

prognathia inferior

widening interdental spaces

broad facial features

T/F because dogs are bigger than cats, they are more affected by mobility/lameness issues resulting from acromegaly

true

acromegaly and cushing's in cats both cause insulin resistance and diabetes mellitus. How can you tell the difference?

cushings: patient skinny with poor haircoat (also, don't really get renal or heart failure in cushings cats)

acromegaly: buff and hairy

how is acromegaly diagnosed in dogs? (2)

IGF-1 levels

history

what other endocrine disorder can appear like acromegaly in dogs?

How can you distinguish them?

Hypothroidism

acromegalous dogs will not have low T4

T/F hypothyroid dogs will have an elevated IGF-1

true

if a dog has an elevated IGF-1 and a low T4, does it have acromegaly or hypothyroidism?

hypothyroidism

how is acromegaly treated in dogs? (3)

stop progestin administration if iatrogenic

neuter

aglepristone (progesterone receptor antagonist)

what is the overall prognosis for dogs with acromegaly?

good

T/F with acromegaly dogs, neither soft tissue or bony changes will resolve with treatment

False; soft tissue changes resolve but bony changes do not

T/F treatment of acromegaly in dogs that also have diabetes due to the acromegaly is one of the rare instances where removing the inciting cause can lead to remission from diabetes in the dog (unlike cats, dogs don't typically spontaneously go into remission with diabetes)

true