Adrenal Disease Flashcards
a 10 yo FS lab presents for recurrent UTIs, PUPD, and increased panting. on urinalysis, the USG is 1.018 and the UPC is 1.5. On blood chemistry she has a high ALT, AST, and ALP. Differentials?
hyperadrenocorticism (cushings)
which kind of cushings is more common in dogs, pituitary or adrenal?
pituitary depndent (85), usually a small pituitary pars distalis tumor.
iatrogenic cushings is caused by
giving steroids for long periods of time
what are the most common clinical signs of cushings in dogs?
PUPD
alopecia
pendulous abdomen
hepatomegaly
polyphagia
pituitary dependent cushings is more common in younger or older dogs? larger or smaller dogs?
younger and small dogs: pituitary
adrenal is often older and bigger dogs
true or false: most cushings dogs come to you happy and not ill
true! some owners might not bring the pet in because their dog seems just fine at home and they think it’s just overweight or changes more common in old dogs like accidents in the house and PUPD
a 12 yo cockapoo comes to you with PUPD, a big belly, and some bilateral alopecia on the flank. You suspect cushings. what changes on chemistry and urinalysis panel would confirm your suspcision?
high ALP, high ALT, hyperlipidemia, USG lower than 1.020, UPC>1 (proteinuria)
list some diferentials for an ALP that is higher than an ALT?
endocrinopathy, diabetes mellitus, cholangitis, cholestatis disease, cholecystolith, steroids, phenobarb, chronic hepatopathies, neoplasia
why do dogs with cushings have a high ALP, high ALT, high lipids, and isosthenuria?
ALP: steroid isoenzyme is induced with cortisol
ALT: swollen hepatocytes and glycogen accumulation
Lipids: lipolysis=high TG and high cholesterol
isosthenuria: diruesis
**note we dont know why they get proteinuria
besides CBC/chem and urinalysis, what are some other diagnostics to confirm cushings in dogs?
blood pressure: many will be hypertensive
urine culture: up to half of dogs have UTIs that are silent due to flushing
screen for hypothyroid, make sure they dont have it
what might you suspect to see on ultrasound in a suspected cushing dog?
hepatomegaly, can check for gallbladder mucocele, can check adrenal gland size
why do cushings dogs show bronchial and tracheal ring mineralization and potential pulmonary thromboembolism?
they are in a hypercoagulable state from the cortisol which increases a bunch of the coagulation factors
what is the difference between a screening test and a differentiating test for cushings? list examples of tests under both categories
screning: do they have cushings or not?
- LDDST (sensitive), ASTH stim (specific), urine cortisol creatinine test (sensitive)
differentiating: what kind of cushing do they have?
- LDDST (4 hr suppression), abdominal ultrasound, HDDST (almost never done anymore)
explain the urine cortisol to creatinine ratio test for cushings
it’s not the best test, although it’s sensitive, it is not very specific (anything causing stress can make it high), I am unlikely to use this test but is an option, owner can bring a urine sample from home
describe the ACTH stim test for cushings
measures the response of adrenal glands in response to ACTH, it tests the adrenal reserve. in cushings dogs they will have an exaggerated response (except if it’s iatrogenic).
You give synthetic ACTH and then collect blood at 1 hour post.
think of the dog knocking on the doors and the doors open and overflow with excess cortisol. adrenals are JACKED ASF
the ACTH stim test is specific but not sensitive, which means
you can miss some cushings but if it’s positive, the patient likely has cushings
true or false: ACTH stim test can differentiate between pituitary and adrenal cushings
false
describe the LDDST 8hr test for cushings?
low dose dex suppression test: the bread + butter test :)
normal animals, if given dex (a steroid), should have negative feedback and suppress ACTH and therefore suppress cortisol
in cushings animals there is little or no suppression
it is sensitive but less specific so if it’s negative it’s less likely to be cushings
proper way to interpret a LDDST?
sample at 4hrs and 8 hrs
look at the 8 hr number first: it’s considered cushings if cortisol is higher than the lab reference
then look at the 4 hr number: most of the time if there is suppression at 4 hr with an increase at 8 hr this indicates pituitary dependent (essentially it dips down and then goes back up, 50% suppression or greater)–>pituitary dependent retains some ability for negative feedback with exoogenous steroids. this does not happen with adrenal dependent
how does an endogenous ACTH test work
with pituitary cushings, endogenous ACTH is high because the pituitary is producing it
with adrenal cushings, endogenous ACTH is low because of the negative feedback and excessice cortisol production
why isn’t the endogenous ACTH test done more?
it’s super expensive and the samples are fragile and need to be shipped in a special vial, it is not practical
the main treatments used for cushings are
trilostane*** and mitotane–>reduce adrenal reserves to what you need. this takes weeks to months to work
could do a hypophysectomy but it’s complicated and not often done
how does trilostane work? what are some potential complications of the drug?
it is a competitive inhibitor of beta hydroxysteroid dehydrogenase enzyme which inhibits the production of progesterone and therefore the production of cortisol (and a little bit aldosterone)
possible adrenal suppression for months if overdosed, adrenal necrosis, mild hyperkalemia from aldosterone suppression, adrenal atrophy
you diagnose a 10 yo dog with cushings and decide to start the dog on trilostane. how will you monitor the dog going forward?
start at 1mg/kg q12 with food, then recheck in 7-10 days, 4-6 hours after the morning dose. We want to see the results of the ACTH stim to be decreased ( we are trying to decrease the adrenal reserves).
if it’s between 70 and 250 and there’s improved clinical signs, keep the dose the same. If it’s between 70 and 250 and there’s no improvement in clinical signs, give it one more month and recheck. If it’s higher than 250, increase dose by 25% and re check in a week. And if it’s below 70, stop the med and start pred (youve given the dog addisons now)
