Diagnosing Hyperadrenocorticism

urine cortisol:creatinine (UCCR)

rule out test

high sensitivity

low specificity

false + are common

can be confident a negative is truly negative

need more tests to confirm

ACTH stimulation

steps

  1. administer synthetic ACTH
  1. take another sample

Cushing's dog exhibit exaggerated response

  1. baseline cortisol

best for pituitary dependent cases

low dose dexamethasone suppression test (LDDSTT)

preferred HAC screening test

steps

  1. baseline cortisol
  1. administer dex
  1. cortisol 4h post
  1. cortisol 8h post

positive dogs have blunted/absent suppression in response

high sensitivity

moderate specificity

as in, remains high

65% have partial suppression though so...that's cool

defined as...

<1.4ug/dL at 4hr

more than 50% baseline at 4-8 hours

differentiation tests

high dose dexamethasone (HDDST)

most cases will suppress

only for differentiation of PDH

specificity poor

10x dose

endogenous ACTH

PDH

ACTH normal to high

tumor constantly producing ACTH regardless of feedback

ADH

ACTH normal to low

abdominal imaging

PDH

bilateral adrenomegaly

ADH

unilateral adrenal mass

small contralateral adrenal

maybe go with this test first

brain MRI if neurologic