Hyperadrenocorticism (Cushing's Dz)

Question 1

Describe the position and function of the adrenal glands

Answer 1

• craniomedially to each kidney
• assist in maintaining blood pressure, electrolyte and water homeostasis, and sexual differentiation; aiding stress response of body

Question 2

Define hyperadrenocorticism

Answer 2

excessive secretion of cortisol

Question 3

2 forms of Cushing’s & what causes them

Answer 3

pituitary-dependent (PDH)
-presence of functional adenoma (usually benign) within the pituitary gland

adrenal-dependent (ADH)
-presence of functional adrenal tumor (benign or malignant)

Question 4

3 general effects of hypercortisolemia upon the body

Answer 4

• 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)

Question 5

List common CS of Cushing’s

Answer 5

• Polyuria w/ compensatory polydipsia
• Polyphagia
• Weight gain
• Pot-bellied appearance
• Alopecia

Question 6

Underlying pathology of Cushing’s CS: polyuria w/ compensatory polydipsia

Answer 6

suspected that cortisol interferes with kidney’s ability to conserve water, resulting in diuresis

Question 7

Underlying pathology of Cushing’s CS: Polyphagia

Answer 7

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

Question 8

Underlying pathology of Cushing’s CS: weight gain

Answer 8

secondary to enlargement of liver (hepatomegaly) as a result of hepatic effects of cortisol

Question 9

Underlying pathology of Cushing’s CS: pot-bellied appearance

Answer 9

mobilization of fat to the abdomen combined with catabolism of muscle proteins and excess abdominal weight leads to sagging of abdominal musculature

Question 10

Underlying pathology of Cushing’s CS: alopecia

Answer 10

unknown; can be very dramatic; often symmetric and non-pruritic

Question 11

Common physical appearance of Cushing’s pet

Answer 11

overweight
pot-bellied
alopecia
hepatomegaly w/ abd. palpaption

Question 12

Cushing’s changes to CBC

Answer 12

stress response leukogram

Question 13

Cushing’s changes to serum chem

Answer 13

+/- 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

Question 14

Cushing’s changes to UA/other urine test

Answer 14

• dilute SG due to polyuria

- Cortisol:creatinine ration –> increased amount of cortisol as compared to urinary creatinine concentration

Question 15

What are the 2 screening lab tests used to determine if Cushing’s is present?

Answer 15

ACTH Stimulation Test

Low Dose Dexamethasone Suppression Test (LDDS)

Question 16

What are ACTH Stim tests results for a Cushing’s patient?

Answer 16

baseline sample will have excess cortisol and post ACTH admin. sample will have even more cortisol

Question 17

LDDST is designed to do what

Answer 17

take advantage of negative feeback system of cortisol upon ACTH

Question 18

How is the LDDST done?

Answer 18

Baseline serum cortisol sample is taken, then an injection of dexamethasone is given followed by 2 additional blood samples at specified times

Question 19

What is dexamethasone?

Answer 19

a synthetic corticosteroid

Question 20

What are the results of a LDDST test in a Cushing’s patient? Explain.

Answer 20

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

Question 21

Mutual con of ACTH stim and LDDST

Answer 21

many outside influences can alter test results and make them difficult to interpret

Question 22

Which test is more resistant to outside influence?

Answer 22

LDDST

Question 23

Which test is more specific?

Answer 23

ACTH Stim

Question 24

How do you determine between PDH and ADH?

Answer 24

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

Question 25

2 Meds for PDH and what they do

Answer 25

Mitotane- causes significant necrosis of all 3 zona layers of adrenal cortex
Trilostane- inhibits adrenal cortex’s ability to produce cortisol

Question 26

Cons of PDH meds

Answer 26

may induce Addison’s if not careful

Question 27

2 therapeutic options for ADH

Answer 27

• surgical removal of adrenal tumor from gland

- mitotane at higher doses than for PDH if not surgical candidate