Hyperadrenocorticism (Cushing's Dz) Flashcards
Describe the position and function of the adrenal glands
- craniomedially to each kidney
- assist in maintaining blood pressure, electrolyte and water homeostasis, and sexual differentiation; aiding stress response of body
Define hyperadrenocorticism
excessive secretion of cortisol
2 forms of Cushing’s & what causes them
pituitary-dependent (PDH)
-presence of functional adenoma (usually benign) within the pituitary gland
adrenal-dependent (ADH)
-presence of functional adrenal tumor (benign or malignant)
3 general effects of hypercortisolemia upon the body
- increased production and mobilization of glucose by the liver and decreased utilization of glucose by the tissues
- promotes catabolism, resulting in decrease in proteins in almost all tissues (exceptions: liver and plasma proteins)
List common CS of Cushing’s
- Polyuria w/ compensatory polydipsia
- Polyphagia
- Weight gain
- Pot-bellied appearance
- Alopecia
Underlying pathology of Cushing’s CS: polyuria w/ compensatory polydipsia
suspected that cortisol interferes with kidney’s ability to conserve water, resulting in diuresis
Underlying pathology of Cushing’s CS: Polyphagia
due to decreased ability of tissues to use glucose for energy, the CNS things that energy is needed; this results in a catabolic state and a constantly hungry pet; also possible that cortisol has direct effect on hunger center
Underlying pathology of Cushing’s CS: weight gain
secondary to enlargement of liver (hepatomegaly) as a result of hepatic effects of cortisol
Underlying pathology of Cushing’s CS: pot-bellied appearance
mobilization of fat to the abdomen combined with catabolism of muscle proteins and excess abdominal weight leads to sagging of abdominal musculature
Underlying pathology of Cushing’s CS: alopecia
unknown; can be very dramatic; often symmetric and non-pruritic
Common physical appearance of Cushing’s pet
overweight
pot-bellied
alopecia
hepatomegaly w/ abd. palpaption
Cushing’s changes to CBC
stress response leukogram
Cushing’s changes to serum chem
+/- mild hyperglycemia due to increased glucose production but decreased glucose utilization
- elevated hepatic enzymes as result of direct effect of cortisol on hepatocytes and hepatic blood flow
- hypercholesterolemia –> lipid metabolism is interfered so there is an increase in circulating cholesterol and triglycerides
Cushing’s changes to UA/other urine test
- dilute SG due to polyuria
- Cortisol:creatinine ration –> increased amount of cortisol as compared to urinary creatinine concentration
What are the 2 screening lab tests used to determine if Cushing’s is present?
ACTH Stimulation Test
Low Dose Dexamethasone Suppression Test (LDDS)
What are ACTH Stim tests results for a Cushing’s patient?
baseline sample will have excess cortisol and post ACTH admin. sample will have even more cortisol
LDDST is designed to do what
take advantage of negative feeback system of cortisol upon ACTH
How is the LDDST done?
Baseline serum cortisol sample is taken, then an injection of dexamethasone is given followed by 2 additional blood samples at specified times
What is dexamethasone?
a synthetic corticosteroid
What are the results of a LDDST test in a Cushing’s patient? Explain.
cortisol level will not change or will be even higher
Reason: a pathological process is inhibiting the negative feedback loop, so the dex doesn’t decrease the cortisol level like in normally would
Mutual con of ACTH stim and LDDST
many outside influences can alter test results and make them difficult to interpret
Which test is more resistant to outside influence?
LDDST
Which test is more specific?
ACTH Stim
How do you determine between PDH and ADH?
Abdominal Ultrasound
- bilateral adrenal gland enlargement = PDH or bilateral adrenal tumor
- unilateral adrenal gland enlargement = suggestive of primary adrenal tumor
Eval of endogenous ACTH concentrations of High Dose Dexamethasone Suppression Test
2 Meds for PDH and what they do
Mitotane- causes significant necrosis of all 3 zona layers of adrenal cortex
Trilostane- inhibits adrenal cortex’s ability to produce cortisol
Cons of PDH meds
may induce Addison’s if not careful
2 therapeutic options for ADH
- surgical removal of adrenal tumor from gland
- mitotane at higher doses than for PDH if not surgical candidate
