Hyperadrenocorticism Flashcards
What is Canine Cushing’s Syndrome?
The constellation of clinical sings/abnormalities resulting from chronic glucocorticoid exposure caused by a tumor in the pituitary (80-85%) or adrenal glands.
Etiology of pituitary dependent hyperadrenocorticism
Excess production of ACTH with loss of negative feedback control on the pituitary
Frequency and amplitude of ACTH secretion is increased
Results in bilateral hyperplasia of the adrenal glands
Etiology of adrenal dependent hyperadrenocorticism
Excessive production of cortisol
Causes negative feedback on the pituitary resulting in suppression of ACTH production
Tumors function independently of hypothalamic/pituitary control
Usually unilateral adrenal involvement - uninvolved adrenal gland develops cortical atrophy as it receives no ACTH stim as a result of negative feedback
Tumor cells in the adrenal gland retain ACTH receptors and therefore may respond to exogenous ACTH
Signalment for hyperadrenocorticism
Mainly dogs
Any breed usually middle aged
More females
PDH - more common in small/toy breeds
ADH - affects large breed dogs more frequently
Prognosis for hyperadrenocorticism
Degree of ALP elevations does not reflect severity of disease or response to treatment
Pituitary microadenomas - good long term prognosis
Pituitary macroadenomas - poor without treatment; fair with effective treatment
Adrenal tumors - good to poor depending on type and tx
Treatment options for adrenal dependent hyperadrenocorticism
Medical
- Trilostane or Mitotane
Surgical
- Adrenalectomy
- can still reoccur in other adrenal gland or can later develop PDH
Goals of treatment for hyperadrenocorticism
Improve quality of life
Eliminate clinical signs
Avoid adverse effects
Medical is treatment of choice for _________ dependent hyperadrenocorticism, and surgical is the the treatment of choice for ___________ dependent hyperadrenocorticism.
Medical - pituitary
Surgical - adrenal
This drug is a chemotherapeutic agent used to treat pituitary dependent hyperadrenocorticism.
Mitotane - adrenolytic; selective necrosis in the zona fasciulata and zona reticular is, often sparing the zona glomerulosa
Adverse effects of Mitotane
Hypoadrenocorticism
Drug induced CNS signs
Can be very severe
This drug used to treat pituitary dependent hyperadrenocorticism is a synthetic steroid analog; enzyme inhibitor that prevents formation of cortisol; competitively inhibits 3 beta hydroxy steroid dehydrogenase
Trilostane
Effects are reversible and dose dependent
Adverse effects of Trilostane
Hypoadrenocorticism
Idiosyncratic adrenal necrosis
GI upset
Mild electrolyte abnormalities due to partial inhibition of aldosterone
Risk of death due to Addisonian crisis
More user friendly but very expensive
Only use Vetoryl brand - compounded has poor efficacy
Protocol for administering Trilostane to treat hyperadrenocorticism
Begin Trilostane tx generally at 1 mg/kg BID or 2 mg/kg SID (increased absorption when given with food)
Recheck ACTH stim / electrolytes at 14 and 30 days and adjust dose as needed
Recheck ACTH stim 10-14 days after any dose adjustment
Are selegilene (MAO inhibitor) and ketoconazole (inhibits steroid production) considered effective treatments for pituitary dependent hyperadrenocorticism?
No
DFDX for an adrenal tumor
Functional adenoma - producing cortisol
Nonfunctional adenoma - doing nothing
Cortical adenocarcinoma - may be functional
Pheochromocytoma - medullary tumor producing catecholamines
Other - metastasis
