cushings Flashcards
HPA feedback loop
CRH from hypothalamus goes positive to pituitary which releases corticotropin which goes positive to the adrenal glands which release cortisol which is negative to pituitary and hypothalamus
cushings
loss of negative feedback, continous of ACTH from pituitary, large adrenals. also releasing
adrenal steroid genesis
starts with cholesterol, many intermediate steps- aldosterone etc. atypical cushings dogs. intermediate thingies. cortisol.
cortisol
usually undulating all day. every 4hrs or so.
adrenal gland three layers.
zona glomerulosa, aldosterone. zona fasciculata, coritsol, zona reitularis, 12 ketosteroids, cortisol. adrenal medulla.
excess cortisol
catabolic. protein. increased glucose output, increase insulin demands, diabetic, bone demineralization. osteoperosis, gi secretion high, creates ulcer. immunosuppress, impair repair of lympocytes. kidney can increased GFR, urine output. PU or cushings. hyperirritable. blood cells, mature neutrophils and platelets and monocytes increase. lymphocytes and eosinophils go down
incidence
older breeds. toy and mini breeds. poodle and dachshunds. avg 8 years
main endogenous causes
pituitary dependent 85-90%- corticotropes, hyperstimulated toproduce acth, or adenoma producing globs of acth. high blood acth, primary adrenal form- adrenal adenocarcinoma. tumor produces cortisol, which shuts off the ACTH. low blood acth
exogenous
be careful tapering, you’ve shut off the adrenals because you’re giving steroids, and this elevates cortisol and shits down acth
physical features
pu/pd, panting, hyperventilation, ascites.muscle laxity in abdominal girdle. pot belly. hair loss, stria/stretch marks. alopecia. hyperpigmentation, acne, bruise easily because lack elasticity of skin, calcinosis cutis– calcium deposit on skin..? dont treat with topical steroids. they go away with time. wrinkles, epidermal atrophy. peeling skin. flaky skin. lethargy polyphagia, muscle weakness, hyperpigmentation of skin and hair, keratin plugging testicular atrophy, hepatomegaly, calcinosis cutis. pulmonary calcification, prothrombic tendency, hypertension, proteinuria, glomerulopathy which might be permanent. same with proteinuria. worry about that. hypercoagulable
lab results
cholesterol, alp, alt, cortisol, elevated. alphos often elevated in cushings, also acth stim. urinalysis– can have bacteruria. proteinuria
cushings imaging
radiography, contrast, U/S CT/MR etc. see in radiology– density appearance in anterior dorsal abdomen. adrenal tumor. calcified mass. mineralized lungs– pathologic calcification from cortisol. impair gas exchange, irreversible.
endocrine diagnosis for cushings
urine cortisol/creatinine ratio. good sensitivity, not so specific. normal is not cushing. good screen, negative rules out cushings. if elevated, rule out pu/pd and invariably do cusghings work up also. ACTH stim test- convenient test does not distinguish. LDDT- distinguish between adrenal/pituitary/HDDT. plasma ACTH.
ACTH stim
stimulating cushing dog goes way up. addisons give you a hypoadreno. or dogs with exogenous steroids.
lo dose dex suppresion
if it suppresses by 4 hours 50%, its pituitary dependent. normal dog will supress after 8 hrs. after 8 hrs it escapes, goes back up. normal dog goes down and stays down. adrenal dog doesn’t go anywhere
